Re: Question About Measuring Wall Declination
I realize that you’ve already gotten good answers, but I’d like to say a few things too. … I’m really late replying, because I’ve been trying to figure out how to word answers to a few long assertion-posts from the usual confused self-sure kids at a philosophical forum. After this time, I’m going to, one way or another, in the forum-options, or my inbox-settings, do a setting that stops topic-announcements from those forums from appearing at my inbox. … First, are you sure that a nail in the wall is the best way? It’s very unlikely to go in perpendicular to the wall. Best would be a block or box that’s reliably rectangular-prism in shape. Lacking that, why not use the short cardboard tube from inside a bathroom-tissue roll? … Assume that the plane of its edge at the ends is perpendicular to its axis & cylindrical-surface. … Stand it on a flat surface, & use a carpenter’s square, a right-triangle drafting square, or a protractor, to mark a vertical line on the tube…or at least the two endpoints of a vertical line. … At the top end of the line, make a small notch, & let that be the shadow-casting point, using the line as the nail. … You’ve got the formula for the declination of a vertical wall, in terms of the measurements of the shadow of a perpendicular object, but you’re interested in the derivation of the solution, & you’ve already gotten good answers about that. But I’d like to make a few comments. … I’m going to refer to the declining-ness of a declining wall, its distance from due-south, as its “facing”, because the word “declination” of course already has a meaning in dialing & astronomy—altitude with respect to the equatorial-plane. … Referring to the spherical coordinate-system whose equatorial-plane is the surface of the declining-wall, I’ll call it the “declining-wall system”. To refer to the spherical coordinate-system whose equatorial plane is the surface of a south-facing wall, I’ll call it the “south-face system”. … This is one of those problems in which, it seems to me, the most computationally-efficient derivation isn’t the most straightforward, obvious, natural easiest one. ...where, in particular, the computationally-efficient derivation uses plane-trigonometry, & the more straightforward easy natural one uses a spherical-coordinate transformation. … Formulas for the length & direction of the nail’s shadow, from the Sun’s position in the coordinate-system with its equator parallel to the wall, can be gotten by coordinate transformations from the Sun’s position in the equatorial co-ordinate-system. … Determine the Sun’s equatorial-coordinates: … The Sun’s hour-angle, its longitude in the equatorial-system, is given by the sundial-time (French hours, equal-hours), the True-Solar Time, gotten from the clock-time by the usual use of the Equation-of-Time & the longitude correction. Hour angle is reckoned clockwise (westward) from the meridian. … The Sun’s declination (altitude in the equatorial-system) for a particular day can be looked up, & interpolated for a particular hour. … It seems to me that the most straightforward solution is to transform the Sun’s equatorial coordinates to the south-face system. … Then transform the Sun’s south-face coordinates to the declining-wall system. … The Sun’s altitude in the declining-wall system gives the length of the shadow, Its longitude in the declining-wall system gives the direction of the shadow on the wall. … You could use the shadow’s length or its direction. The shadow’s length, from the Sun’s altitude in the declining-wall system, has a briefer formula, & the length of the shadow is easier to measure than its direction. …& so I’ll speak of using the length of the shadow. … Resuming: When you’ve transformed the Sun’s south-face coordinates to declining-wall coordinates, the resulting formula for the Sun’s altitude in the declining-wall system will include a variable consisting of the angle between one system’s pole & the other system’s equatorial-plane. (That’s the latitude when you’re converting between the horizontal & equatorial systems, & so I call it the “latitude” for any coordinate transformation. That’s what I mean by “latitude”, in quotes, here) … Solve that formula for the “latitude”. Evaluate the “latitude”. Subtract that from 90 degrees, to get the wall’s facing. …thje amount by which it declines. … This assumes that the wall declines by less than 90 degrees. … Incidentally, this isn’t the only problem in which coordinate-transformations seem more straightforward than the plane-trigonometry solution: … I once noticed that a vertical-declining dial can be marked by plane trigonometry, but spherical coordinate-transformations seem more straightforward. … Likewise, it seems to me that the marking of the declination-lines for a Horizontal-Dial can be done most computationally-efficiently by plane trigonometry at the dial., …but calculating the Sun’s altitude & azimuth for each
Re: Adjusting dial to new location
I mentioned several alignments, the correction of any one of which could be used to determine how much the dial-plate should be rotated in its own plane (either before or after the tip). Most recently I suggested the altitude of the pointing-direction of the style. But it seems to me that it would be easier to correct the pointing-direction of the noon-line to the hour-angle equal to 180 degrees + the westward longitude-offset (the amount by which you want the LTST o a longitude west of yours…& of course negative if you want it for a longitude east of yours). In my example, the longitude-offset way7 degrees. That correction gives a simpler expression for the necessary dial-plate rotation in its own plane. (…which can be done before or after the tip). On Tue, Apr 11, 2023 at 08:52 Michael Ossipoff wrote: > I retract the addendum. I wrote it with the notion that the noon-line > should be under the style. …as if the dial were intended to read for its > own longitude. > > So, sorry—disregard the addendum (…as you probably already have). > > The dial-plate’s rotation in its own plane should be to correct the > style’s pointing-direction (in altitude or azimuth), as I originally said & > described. > > Correcting its altitude would give an easier equation-solution. > > > > On Sat, Apr 8, 2023 at 21:25 Michael Ossipoff > wrote: > >> Addendum: >> >> … >> >> Instead of finding the dial-plate rotation in its own plane that corrects >> the style’s pointing-direction, it might be easier to, instead, find the >> dial-plate rotation in its own plane that puts the dial’s noon-line in the >> meridianal-plane….i.e. gives that noon-line an azimuth of zero. >> > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
I retract the addendum. I wrote it with the notion that the noon-line should be under the style. …as if the dial were intended to read for its own longitude. So, sorry—disregard the addendum (…as you probably already have). The dial-plate’s rotation in its own plane should be to correct the style’s pointing-direction (in altitude or azimuth), as I originally said & described. Correcting its altitude would give an easier equation-solution. On Sat, Apr 8, 2023 at 21:25 Michael Ossipoff wrote: > Addendum: > > … > > Instead of finding the dial-plate rotation in its own plane that corrects > the style’s pointing-direction, it might be easier to, instead, find the > dial-plate rotation in its own plane that puts the dial’s noon-line in the > meridianal-plane….i.e. gives that noon-line an azimuth of zero. > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
For complete generality: If your sundial was made for a latitude greater then yours by an amount called “DeltaLat” (which could be positive or negative), & if you want the dial to give LTST for a longitude 7 degrees west of yours (maybe because that’s your standard-meridian), then: After the tip, the initially-top-point of the sphere with a great-circle coinciding with the circumference of your circular dial-plate will have equatorial-coordinates of: (Lat+DeltaLat, 7). After that, it’s exactly as I said. On Sun, Apr 9, 2023 at 14:09 Steve Lelievre wrote: > > On 2023-04-08 8:52 p.m., Michael Ossipoff wrote: > > I know you said you wanted a link, not instructions, but people have been > suggesting how to achieve dial-autocorrection to Local True Solar Time > (LTST) at the standard-meridian, instead of one’s own meridian. So I felt > that it would be justified to comment about it. > > Michael, > > To me, your case seems to be a specific instance that is covered by the > general case - have I missed something? > > As things stand, I think I know the math involved because I have from the > article by Fred Sawyer that I mentioned in a previous email. It describes > the solution for the general case - we start with a dial at some latitude > and longitude that shows the solar time at some other longitude, which may > or may not be zero offset. We want to move it to a new latitude and > longitude and to show the solar time at some new 'other' longitude, which > may or may not have zero offset from the new location. As well, the article > by Fabio Savian, mentioned in his post, also discusses dial relocation. > (BTW, for NASS members, Fabio only mentioned his article in its Italian > version, but as well he kindly provided an English equivalent which was > included in the most recent issue of the Compendium) > Everyone, > > Since I'm writing this post, I'll take the opportunity to mention that I > have made a couple of small adjustments to my online wedge calculator, > gnomoni.ca/wedge . My thanks go to Roderick Wall for helping me make it > better for the southern hemisphere. Please let me know if you spot any > issues. > > > Steve > > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
Yes, I spoke of a special-case in which you’re 7 degrees east of your standard-meridian. …for a concrete example. But the rest of what I said was for the general-case in which you want the dial to read in the LTST at your standard-meridian. But yes, I didn’t speak of when the dial is made for a different latitude *and* you want standard-meridian LTST. I thought that it was just about getting the standard- meridian LTST. …something I wouldn’t do anyway. On Sun, Apr 9, 2023 at 14:09 Steve Lelievre wrote: > > On 2023-04-08 8:52 p.m., Michael Ossipoff wrote: > > I know you said you wanted a link, not instructions, but people have been > suggesting how to achieve dial-autocorrection to Local True Solar Time > (LTST) at the standard-meridian, instead of one’s own meridian. So I felt > that it would be justified to comment about it. > > Michael, > > To me, your case seems to be a specific instance that is covered by the > general case - have I missed something? > > As things stand, I think I know the math involved because I have from the > article by Fred Sawyer that I mentioned in a previous email. It describes > the solution for the general case - we start with a dial at some latitude > and longitude that shows the solar time at some other longitude, which may > or may not be zero offset. We want to move it to a new latitude and > longitude and to show the solar time at some new 'other' longitude, which > may or may not have zero offset from the new location. As well, the article > by Fabio Savian, mentioned in his post, also discusses dial relocation. > (BTW, for NASS members, Fabio only mentioned his article in its Italian > version, but as well he kindly provided an English equivalent which was > included in the most recent issue of the Compendium) > Everyone, > > Since I'm writing this post, I'll take the opportunity to mention that I > have made a couple of small adjustments to my online wedge calculator, > gnomoni.ca/wedge . My thanks go to Roderick Wall for helping me make it > better for the southern hemisphere. Please let me know if you spot any > issues. > > > Steve > > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
Addendum: … Instead of finding the dial-plate rotation in its own plane that corrects the style’s pointing-direction, it might be easier to, instead, find the dial-plate rotation in its own plane that puts the dial’s noon-line in the meridianal-plane….i.e. gives that noon-line an azimuth of zero. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
Steve— … I know you said you wanted a link, not instructions, but people have been suggesting how to achieve dial-autocorrection to Local True Solar Time (LTST) at the standard-meridian, instead of one’s own meridian. So I felt that it would be justified to comment about it. … …even though that autocorrection wouldn’t bring any convenience for the user, who’d still need a correction (for Eqt), & even though it would create an inconvenience for anyone who wanted genuinely local LTST, because they’d have to uncorrect the longitude-correction. … First I suggested solution of 3 simultaneous nonlinear equations, written via coordinate-transformation formulas, with three unknown variables: Initial horizontal dial-plate rotation about the vertical axis through its center, the place on the dial-plate circumference for placing the wedge, & the amount to tip the plate with that wedge. … …in order to get the style pointed at the celestial-pole, with the noon-line in the meridianal-plane. 3 equations in 3 unknowns. … Undeniably that would solve the problem, but 3 nonlinear equations would be a bit of work. That work is unnecessary, because it can be solved analytically. … I described how one could find how to tip the dial-plate: … 1) The point at the top of the sphere having a great-circle that coincides with the circumference of the dial-plate, has, in the equatorial-coordinate-system, a declination equal to the latitude of the dial. It has an hour-angle (equatorial longitude) of zero. … 2) Say you’re 7 degrees east of your standard meridian. Rotating the dial 7 degrees westward about the polar axis, the axis of the equatorial-system, changes the top-point’s equatorial coordinates to (Lat, 7). … 3) Transform those new equatorial coordinates to the horizontal coordinate system, to get the altitude & azimuth of the top-point. … 4) Place the wedge at the edge of the circular dial-plate 180 degrees from the calculated azimuth of the top point. Tip the dial-plate up, there, by an angle equal to the complement of the calculated altitude of the top-point. … Now the dial-plate is tipped as it would be if the dial had been rotated 7 degrees westward in equatorial-longitude, hour-angle, about the polar-axis. But the dial’s noon-line might not be in the meridianal-plane. … One way to fix that: … 5) Rotate the dial-plate in the plane of the dial-face, until the dial reads the correct LTST at the standard-meridian. … That would require carefully marking where the edge of the dial place is, at several circumference-positions on the table-surfa ce, marking where the wedge with respect to dial & table-surface, & marking where the dial-plate touches the wedge. … Then lift the dial-plate a bit off the wedge & rotate the dial-plate in the plane of its dial-surface, & set it back down, making sure that the dial-plate & wedge are at their original marks. … Do that till the dial reads the LTST at the standard-meridian. … That dial-rotation sounds laborious & awkward, doing it after the tipping, with all the position marking & keeping. …especially with the wedge under the dial-plate. … Another way: … 6) Before the tipping, the style is pointing at the celestial-pole. Transform that position to the get the pole’s pre-tip coordinates in the coordinate system whose axis is a horizontal line perpendicular to the direction in which the direction in which the dial is going to be tipped. Now add the complement of the calculated top-point-altitude to the longitude in that system with the horizontal axis. That gives the style’s pointing-direction’s new longitude in the system with the horizontal tip-axis. So now you have both of its new coordinates in that system. … 7) Transform that position to either the horizontal (altazimuth) coordinate-stem, to get the altitude & azimuth of the style’s new pointing-direction…or instead to the equatorial-system to get the style’s pointing-direction, as declination & hour-angle in the equatorial-system. … 8) That tells you how much the style’s pointing-direction is off, in terms of its altitude, or its azimuth, or its declination. …whichever of those you want to use. Its azimuth should of course be zero. Its altitude should of course equal your latitude, & its declination of course should be 90 degrees. The altitude is probably not a good choice to use, because it changes more slowly with change in the dial plate rotation. I’d probably use the declination, because its formula is simpler than that of the azimuth. … 9) So, find out how much thequantity for the style’s pointing-direction that you’re using, say the declination, needs to change, to put it where it should be. Another coordinate-transformation will tell you how much the dial-plate would have to rotate in the plane of the dial-face, to achieve that. That’s the desired dial-plate-rotation. … 10) So, before tipping, you rotate the dial-plate in its own plane, by that amount, before you
Re: Adjusting dial to new location
Contrary to what I suggested yesterday, the adjustment of a sundial to give LTST at the standard-meridian doesn’t require solution of a system of equations. It’s a straightforward coordinate-transformation: … Say the dial-plate is circular. For a sphere that circumscribes that dial-plate, the equatorial-coordinates on the sphere, of a point at the top of that sphere, are (Lat, 0). ... …where Lat is the latitude of the dial’s location, & 0 is defined as the longitude of the topmost meridian in the equatorial-system. … Now, say your location is 7 degrees east of your standard meridian. You want to change the equatorial-coordinates of that top-point to (Lat, 7). ... (…because let’s say that hour-angle (equatorial-longitude) is measured clockwise (westward) from the NS meridian, as it normally is.) … That’s the top-points coordinates in the equatorial system when the sphere has been rotated 7 degrees about its polar-axis, toward the standard-meridian. ... Now transform the top-point’s coordinates (Lat, 7) to the horizontal coordinate-system. … That gives you the azimuth & altitude of the top-point, as seen from the center of the sphere. … The dial-edge is a great circle on the sphere, all of which is 90 degrees away from the former top-point. … The place on the dial-plate that should be raised is the place 180 degrees from the top-point’s azimuth. … Raise that point by an angle equal to the complement of the altitude of the top-point On Sun, Mar 26, 2023 at 5:30 PM Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > Hi, > > Can anyone point me to an existing online calculator for making a wedge > to adjust a horizontal dial to a new latitude and longitude? > > I am not asking for an explanation of how to do the calculation; I just > want to be able to point people to a calculator that has already been > proved on the internet. It should use the original location (latitude > and longitude) and the new location to calculate the angle of slope of > the wedge and the required rotation from the meridian. > > Many thanks, > > Steve > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
The dial produces a shadow. The hour lines and other indications are strictly our interpretation and a particular one should not be forced on everybody else [/quote] … I didn’t force anything on you. I expressed my preference, & I asked why anyone would want a dial to directly read the LTST at the standard-meridian instead of where you are, & I told why that modification doesn’t make it any easier to obtain clock-time, but does make the dial require a correction for local LTST. On Tue, Apr 4, 2023 at 7:17 PM wrote: > Assuming that a dial should read only local solar time is a rather limited > view. While it might be of interest to the dial purist, it is not > particularly useful to the general population and often requires a lot of > explanation. And it makes us seem like an eccentric clique. The dial > produces a shadow. The hour lines and other indications are strictly our > interpretation and a particular one should not be forced on everybody else. > --- > > > > On 2023-04-04 13:05, Michael Ossipoff wrote: > > > > On Tue, Apr 4, 2023 at 08:45 wrote: > > Rotating the dial plate around a vertical axis is wrong because the hours > lines are not at constant angles. > > Rotating the whole dial around the polar axis is the correct way to adjust > a local solar time dial to a different longitude, the time zone center, for > example. > > Having a dial show the time in a different location is strictly a creative > choice. > --- > > > Rotating the dial about the vertical axis & then doing the non-meridian Al > tipping, in the right combination, is how you get the result that the dial > is oriented (still in the meridianal-plane) to give Local True Solar Time > at your standard meridian. > > > I don't know why anyone would want to do that, unless it's important to > keep using an old EqT plaque. > > > > On 2023-04-04 08:44, Jack Aubert via sundial wrote: > > Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die > eigentliche Nachricht steht dadurch in einem Anhang. > > This message was wrapped to be DMARC compliant. The actual message > text is therefore in an attachment. > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
By “auto-correction”, I refer modification of the dial, so that it will directly read Local-True-Solar-Time (LTST) at your latitude at your standard-meridian instead of where the dial is. … Auto-correcting for longitude by rotating & tipping the dial is a “retrofit” longitude auto-correction, as opposed to initially incorporating that auto-correction in the marking of the dial. … (As I said, I have no idea why anyone would want longitude-auto-correction, to make the dial read the Local-True-Solar-Time (LTST) at your latitude at your timezone’s standard-meridian (instead of where the dial is). Because the longitude-correction could be achieved by merely adding the longitude-correction constant to each EqT entry on the correction-plaque, the auto-correction doesn’t avoid any table-consulting & correction work needed by the dial-user who wants standard-time. All it accomplishes is to make LTST determination require a correction too.) … As has already been pointed out twice, only one wedge is needed. … The longitude-correction could be achieved by, first, an initial rotation about the vertical axis, & then a rotation about some particular horizontal axis. … Three variables: … 1. The amount & direction of initial rotation, about the vertical-axis, away from the NS alignment of the gnomon. … 2. The place on the circular-dial-plate’s circumference at which the wedge is applied. … 3. The amount by which the dial-plate is tipped by that wedge. … There are three desiderata: … 1. The style is in the meridianal-plane, with its higher end poleward. … 2.The Style is tipped above the horizontal by an angle equal to the latitude. … 3. The dial has been rotated about the style so as to have the orientation of flat ground at your standard-parallel.at your latitude. (i.e. rotated in the direction of your standard meridian, by the number of degrees by which that meridian differs from yours.) … Those 3 desiderata give 3 equations in 3 unknowns. The 3 variable are the unknowns. … The equations are spherical co-ordinate-transformation formulas. The 3 equation are statements, in terms of those formulas, that the 3 desiderata are achieved. … The 3 nonlinear equations in 3 unknowns can be numerically-solved by the Newton-Raphson method, In fact according to some authors, Newton-Raphson is the only method available for a system of nonlinear equations. … You speak of rotation about 3 axes. …2 of them by wedges? (…because you’ve suggested 2 wedges.). ,,, When the 1st wedge is put in at (say) the dial-plate’s north edge, the dial plate is supported by, & stably balanced on, the wedge at the dial-plate’s north edge, & the dial edge opposite the wedge, at the south edge of the dial-plate. That means that the whole dial-plate & all of its periphery (except its south-point) are above the horizontal table-surface on which the dial was resting. … Now, when you put a 2nd wedge in at (say) the dial-plate’s east edge, & push it in till it contacts the raised dial-edge, & then & start rotating the dial-plate with it, about what axis are you rotating the dial-plate? You’re rotating it about the line drawn between the point at the dial-plate’s south edge, where the dial-plate rests on its horizontal table, & some point on the west edge of the wedge at the north end of the dial. … That isn’t a horizontal axis. … I guess you could do it that way, but it sounds like more work than the use of just one wedge. … As I said, you only need one wedge. … Your other suggestion expressed after that is unclear. On Tue, Apr 4, 2023 at 7:38 PM wrote: > Depending on your choice of rotation axes, only two rotations are needed, > one for the elevation of the pole and one around the gnomon for longitude > correction. These are the two that correspond to the actual changes needed. > > If you are using the three orthogonal x, y, and z axes, then three > rotations are needed. And they can tell you how to make the wedge. > > Another three rotation procedure that might be easier to understand but > may not tell you how to make the wedge is this. Rotate about a horizontal > axis until the gnomon is vertical. Now rotate around the vertical axis to > include the longitude correction. Then rotate around a horizontal axis to > put the gnomon in the correct new location. I would do this in a computer > graphics situation because it only requires the old and new position values. > --- > > > > On 2023-04-04 15:54, Steve Lelievre wrote: > > > At a new location, a dial must end up with the style parallel to the polar > axis - but how do you achieve that using a wedge? Assuming you start with > the dial at the new location on a horizontal surface with the sub-stile > line on the local meridian, the required sequence is to rotate it about the > local vertical, then about an east-west line, and then about the vertical > again. Perhaps this helps visualize it... https://youtu.be/mtEgSXJPXSw > > The wedge achieves the same thing
Fwd: Adjusting dial to new location
-- Forwarded message - From: Michael Ossipoff Date: Tue, Apr 4, 2023 at 09:53 Subject: Re: Adjusting dial to new location To: The combination of rotation about the vertical axis, & then non-meridianal tipping, hadn’t occurred to me. …to directly read the Local True Solar Time of somewhere else. …so that you can just use your old EqT plaque after you move? Wouldn’t have occurred to me. I’d just make a table incorporating EqT & the new longitude- correction. I wouldn’t want a sundial to be committed to clock-time, by building in the longitude correction (either when marking the dial, or by the rotation & tipping). On Tue, Apr 4, 2023 at 08:45 wrote: > Rotating the dial plate around a vertical axis is wrong because the hours > lines are not at constant angles. > > Rotating the whole dial around the polar axis is the correct way to adjust > a local solar time dial to a different longitude, the time zone center, for > example. > > Having a dial show the time in a different location is strictly a creative > choice. > --- > > > > On 2023-04-04 08:44, Jack Aubert via sundial wrote: > > Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die > eigentliche Nachricht steht dadurch in einem Anhang. > > This message was wrapped to be DMARC compliant. The actual message > text is therefore in an attachment. > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
The public stationary sundial in my town is mounted normally for Local True Solar Time. It’s correction-plaque gives un-adjusted EqT, with an instruction to add a certain number of minutes for the longitude-correction. On Sun, Apr 2, 2023 at 17:26 Steve Lelievre wrote: > You don’t need two wedges, you just skew the positioning to do both > adjustments in one. > > If you have The Compendium vol 7 issue 1, take a look at the articles by > Fred Sawyer and Bill Gottesman. > > Steve > > On Sun, Apr 2, 2023 at 17:20, Rod Wall wrote: > >> Hi Jack and Steve, >> >> To implement what Jack has indicated. You could have two wedges one on >> top of each other. One for Latitude correction and one for Longitude >> correction. >> >> You could also just use a Longitude correction wedge if you only wanted >> to correct for Longitude. >> >> When writing instructions. Please also include people who live in the >> southern hemisphere, we do also have sundials. >> >> Do I have this correct? >> >> Roderick. >> >> On 3/04/2023 9:24 am, Steve Lelievre wrote: >> >> Jack, >> >> Try out my calculator! You can specify a time zone meridian for the dial >> at its original location, or at its new location, or both. If there is an >> effective longitude change, it'll tell you how to position (twist) the dial >> on the wedge and how to orient the wedge itself, turning it away (rotating >> it ) from the meridian line. >> >> Steve >> >> >> On 2023-04-02 3:59 p.m., Jack Aubert wrote: >> >> I thought about this briefly. I had always thought that the purpose of >> the shim or wedge adjustment was to tip the dial north or south so that >> dial is at the latitude it was originally designed for. If the original >> dial has a built-in longitude correction, that could also be factored into >> a wedge which would have both a north-south and east-west axis. But a >> wedge would not work if it moved the gnomon out of alignment with the with >> the rotation of the earth (or the celestial sphere). I think a >> longitudinal adjustment would only work if he original dial had a time-zone >> offset included by rotating the hour lines with respect to the origin of >> the gnomon. >> >> >> >> Does this make sense? It sounds like a good project for a 3-D printer. >> >> >> >> Jack >> >> >> >> *From:* sundial >> *On Behalf Of *Steve Lelievre >> *Sent:* Sunday, April 2, 2023 5:16 PM >> *To:* Michael Ossipoff >> *Cc:* Sundial List >> *Subject:* Re: Adjusting dial to new location >> >> >> >> Michael, >> >> Yes, I recognize that to get Mean Time involves Equation of Time >> adjustment and that Equation of Longitude can be handled there to give >> Standard Time (or DST). >> >> But anyway, my inquiry was to seek an online wedge calculator. Nobody >> identified one and a week seemed an adequate wait for responses, so I've >> just written one. Anyone who's interested, please see >> >> >> https://sundials.org/index.php/teachers-corner/sundial-construction/367-easy-dial-adjustment-for-your-latitude >> >> Cheers, >> >> Steve >> >> >> >> On 2023-04-02 1:41 p.m., Michael Ossipoff wrote: >> >> I just want to mention that the shim under the north or south edge of the >> dial is only for latitude. Longitude is corrected-for by changing the >> constant term of the Sundial-Time to Clock-Time conversion. >> >> >> >> But usually Sundial-Time, Local True Solar Time, is what I’d want from a >> sundial. >> >> >> >> On Sun, Mar 26, 2023 at 14:30 Steve Lelievre < >> steve.lelievre.can...@gmail.com> wrote: >> >> Hi, >> >> Can anyone point me to an existing online calculator for making a wedge >> to adjust a horizontal dial to a new latitude and longitude? >> >> I am not asking for an explanation of how to do the calculation; I just >> want to be able to point people to a calculator that has already been >> proved on the internet. It should use the original location (latitude >> and longitude) and the new location to calculate the angle of slope of >> the wedge and the required rotation from the meridian. >> >> Many thanks, >> >> Steve >> >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> ---https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> -- > Cell +1 778 837 5771 > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
On Tue, Apr 4, 2023 at 08:45 wrote: > Rotating the dial plate around a vertical axis is wrong because the hours > lines are not at constant angles. > > Rotating the whole dial around the polar axis is the correct way to adjust > a local solar time dial to a different longitude, the time zone center, for > example. > > Having a dial show the time in a different location is strictly a creative > choice. > --- > > > Rotating the dial about the vertical axis & then doing the non-meridian Al > tipping, in the right combination, is how you get the result that the dial > is oriented (still in the meridianal-plane) to give Local True Solar Time > at your standard meridian. > I don’t know why anyone would want to do that, unless it’s important to keep using an old EqT plaque. > On 2023-04-04 08:44, Jack Aubert via sundial wrote: > > Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die > eigentliche Nachricht steht dadurch in einem Anhang. > > This message was wrapped to be DMARC compliant. The actual message > text is therefore in an attachment. > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
That surprises me too. I’d have expected that the only differences would be that the dial is numbered counterclockwise, & that north & & south are replaced with poleward & equatorward. On Mon, Apr 3, 2023 at 16:47 Steve Lelievre wrote: > Hi, Roderick, > > My home internet connection is still non-functional so I can't fix it yet, > but it does seem that I will have to add an extra test to handle southern > hemisphere locations and reducing latitudes. Actually, I originally had a > southern hemisphere check in there but took it out after convincing myself > the same frame of reference (x axis east, y axis north, z up) applied to > the spherical trigonometry irrespective of hemisphere. Ho hum. > > Steve > > > On 2023-04-03 6:45 a.m., Rod Wall wrote: > > Hi Steve, > > For both examples below with all sundials at the same Longitude. The > instructions indicate: > > Place the wedge-sundial assembly on a horizontal surface in a nice sunny > location. *Start with the higher end of the wedge to the north* and the > sides aligned on a north-south line and the sharp edge should be on an > east-west line. > > Example 1: > > If you have a sundial that was designed for Latitude -20 deg. And relocate > it at Latitude -50 deg. > > Would you start with the higher end of the 30 deg wedge to the North. Or > would it be to the South? > > * > > Example 2: > > If you have a sundial that was designed for Latitude 50 deg. And relocate > it at 20 deg. > > Would you start with the higher end of the 30 deg wedge to the North. Or > would it be to the South? > > * > > Please correct me if I am wrong. I think that both examples would be to > the South. > > Roderick. > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Fwd: Adjusting dial to new location
-- Forwarded message - From: Date: Mon, Apr 3, 2023 at 07:35 Subject: Re: Adjusting dial to new location To: Michael Ossipoff Local Solar Time is one of the things that a dial can do. But I might want Time Zone time. Or I might want Paris France time. A dial can do both with a longitude correction. When making a sundial intended for use at just one location (e.g. a stationary dial or a portable tablet horizontal dial), I combine EqT & longitude correction into a single correction-table. When all watches were mechanical, & reliable accurate ones were expensive, I used to carry & use a tablet dial, made of corrugated box-cardboard, aligned with a compass embedded in the dial-face. With the combined-correction on the top of the closed tablet-dial. --- On 2023-04-02 21:40, Michael Ossipoff wrote: On Sun, Apr 2, 2023 at 18:31 wrote: I tried the app. I used 40, -75 and 45, -70. It just said to use a 5 degree wedge and said nothing about a longitude correction. I communicated to Steve privately last week. I said that a longitude correction was a rotation around the gnomon. Does anybody else believe this? One of the books, I can't remember which, calls this The Universal Sundial Principle. It says that two dials with the same orientation in space with respect to the sun will read the same time, regardless of where on earth they are. Yes, & if you want Local True Solar Time, then you don't need longitude correction or Equation of Time. --- If you want clock-time, then use the EqT, & add 4 minutes for each degree west of your standard meridian. But isn't Sundial Time (Local True Solar Time) what you want from a sundial? On 2023-04-02 19:24, Steve Lelievre wrote: Jack, Try out my calculator! You can specify a time zone meridian for the dial at its original location, or at its new location, or both. If there is an effective longitude change, it'll tell you how to position (twist) the dial on the wedge and how to orient the wedge itself, turning it away (rotating it ) from the meridian line. Steve On 2023-04-02 3:59 p.m., Jack Aubert wrote: I thought about this briefly. I had always thought that the purpose of the shim or wedge adjustment was to tip the dial north or south so that dial is at the latitude it was originally designed for. If the original dial has a built-in longitude correction, that could also be factored into a wedge which would have both a north-south and east-west axis. But a wedge would not work if it moved the gnomon out of alignment with the with the rotation of the earth (or the celestial sphere). I think a longitudinal adjustment would only work if he original dial had a time-zone offset included by rotating the hour lines with respect to the origin of the gnomon. Does this make sense? It sounds like a good project for a 3-D printer. Jack *From:* sundial *On Behalf Of *Steve Lelievre *Sent:* Sunday, April 2, 2023 5:16 PM *To:* Michael Ossipoff *Cc:* Sundial List *Subject:* Re: Adjusting dial to new location Michael, Yes, I recognize that to get Mean Time involves Equation of Time adjustment and that Equation of Longitude can be handled there to give Standard Time (or DST). But anyway, my inquiry was to seek an online wedge calculator. Nobody identified one and a week seemed an adequate wait for responses, so I've just written one. Anyone who's interested, please see https://sundials.org/index.php/teachers-corner/sundial-construction/367-easy-dial-adjustment-for-your-latitude Cheers, Steve On 2023-04-02 1:41 p.m., Michael Ossipoff wrote: I just want to mention that the shim under the north or south edge of the dial is only for latitude. Longitude is corrected-for by changing the constant term of the Sundial-Time to Clock-Time conversion. But usually Sundial-Time, Local True Solar Time, is what I'd want from a sundial. On Sun, Mar 26, 2023 at 14:30 Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: Hi, Can anyone point me to an existing online calculator for making a wedge to adjust a horizontal dial to a new latitude and longitude? I am not asking for an explanation of how to do the calculation; I just want to be able to point people to a calculator that has already been proved on the internet. It should use the original location (latitude and longitude) and the new location to calculate the angle of slope of the wedge and the required rotation from the meridian. Many thanks, Steve --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Fwd: Adjusting dial to new location
-- Forwarded message - From: Michael Ossipoff Date: Mon, Apr 3, 2023 at 14:12 Subject: Re: Adjusting dial to new location To: Of course, but I’d always make the dial to directly show Local True Solar Time. I’d never incorporate a built-in longitude correction. My use of EqT & longitude- correction constant is only for: 1. Aligning the dial by use of a clock or watch 2. Getting Local True Solar Time from a clock or watch 3. Determine the clock-time of a sunset, end of evening civil-twilight, or beginning of morning nautical-twilight On Mon, Apr 3, 2023 at 07:35 wrote: > Local Solar Time is one of the things that a dial can do. But I might want > Time Zone time. Or I might want Paris France time. A dial can do both with > a longitude correction. > > > --- > > > > On 2023-04-02 21:40, Michael Ossipoff wrote: > > > > On Sun, Apr 2, 2023 at 18:31 wrote: > > I tried the app. I used 40, -75 and 45, -70. It just said to use a 5 > degree wedge and said nothing about a longitude correction. > > I communicated to Steve privately last week. I said that a longitude > correction was a rotation around the gnomon. Does anybody else believe > this? One of the books, I can't remember which, calls this The Universal > Sundial Principle. It says that two dials with the same orientation in > space with respect to the sun will read the same time, regardless of where > on earth they are. > > > Yes, & if you want Local True Solar Time, then you don't need longitude > correction or Equation of Time. > --- > If you want clock-time, then use the EqT, & add 4 minutes for each degree > west of your standard meridian. > > > But isn't Sundial Time (Local True Solar Time) what you want from a > sundial? > > > > > > On 2023-04-02 19:24, Steve Lelievre wrote: > > Jack, > > Try out my calculator! You can specify a time zone meridian for the dial > at its original location, or at its new location, or both. If there is an > effective longitude change, it'll tell you how to position (twist) the dial > on the wedge and how to orient the wedge itself, turning it away (rotating > it ) from the meridian line. > > Steve > > > On 2023-04-02 3:59 p.m., Jack Aubert wrote: > > I thought about this briefly. I had always thought that the purpose of > the shim or wedge adjustment was to tip the dial north or south so that > dial is at the latitude it was originally designed for. If the original > dial has a built-in longitude correction, that could also be factored into > a wedge which would have both a north-south and east-west axis. But a > wedge would not work if it moved the gnomon out of alignment with the with > the rotation of the earth (or the celestial sphere). I think a > longitudinal adjustment would only work if he original dial had a time-zone > offset included by rotating the hour lines with respect to the origin of > the gnomon. > > > > Does this make sense? It sounds like a good project for a 3-D printer. > > > > Jack > > > > *From:* sundial > *On Behalf Of *Steve Lelievre > *Sent:* Sunday, April 2, 2023 5:16 PM > *To:* Michael Ossipoff > *Cc:* Sundial List > *Subject:* Re: Adjusting dial to new location > > > Michael, > > Yes, I recognize that to get Mean Time involves Equation of Time > adjustment and that Equation of Longitude can be handled there to give > Standard Time (or DST). > > But anyway, my inquiry was to seek an online wedge calculator. Nobody > identified one and a week seemed an adequate wait for responses, so I've > just written one. Anyone who's interested, please see > > > https://sundials.org/index.php/teachers-corner/sundial-construction/367-easy-dial-adjustment-for-your-latitude > > Cheers, > > Steve > > > On 2023-04-02 1:41 p.m., Michael Ossipoff wrote: > > I just want to mention that the shim under the north or south edge of the > dial is only for latitude. Longitude is corrected-for by changing the > constant term of the Sundial-Time to Clock-Time conversion. > > > But usually Sundial-Time, Local True Solar Time, is what I'd want from a > sundial. > > > On Sun, Mar 26, 2023 at 14:30 Steve Lelievre < > steve.lelievre.can...@gmail.com> wrote: > > Hi, > > Can anyone point me to an existing online calculator for making a wedge > to adjust a horizontal dial to a new latitude and longitude? > > I am not asking for an explanation of how to do the calculation; I just > want to be able to point people to a calculator that has already been > proved on the internet. It should use the original location (latitude > and longitude) and the new location to calculate the angle of slope of > the
Fwd: Adjusting dial to new location
-- Forwarded message - From: Michael Ossipoff Date: Mon, Apr 3, 2023 at 14:04 Subject: Re: Adjusting dial to new location To: Rod Wall Yes, because you’ve moved the dial south, you tip it south. The wedge-use is as you say, but I’d prefer a flat, vertical-edge shim, because it wouldn’t experience a force tending to push it out. On Mon, Apr 3, 2023 at 06:45 Rod Wall wrote: > Hi Steve, > > For both examples below with all sundials at the same Longitude. The > instructions indicate: > > Place the wedge-sundial assembly on a horizontal surface in a nice sunny > location. *Start with the higher end of the wedge to the north* and the > sides aligned on a north-south line and the sharp edge should be on an > east-west line. > > Example 1: > > If you have a sundial that was designed for Latitude -20 deg. And relocate > it at Latitude -50 deg. > > Would you start with the higher end of the 30 deg wedge to the North. Or > would it be to the South? > > * > > Example 2: > > If you have a sundial that was designed for Latitude 50 deg. And relocate > it at 20 deg. > > Would you start with the higher end of the 30 deg wedge to the North. Or > would it be to the South? > > * > > Please correct me if I am wrong. I think that both examples would be to > the South. > > Roderick. > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
Tipping the dial-plate for latitude makes it exactly as if the dial were at the latitude it was made for. No need for a 2nd wedge. If the new longitude differs from the old on, then just adjust your longitude correction constant. + 4 minutes for every degree more west of your standard meridian. On Sun, Apr 2, 2023 at 17:20 Rod Wall wrote: > Hi Jack and Steve, > > To implement what Jack has indicated. You could have two wedges one on top > of each other. One for Latitude correction and one for Longitude correction. > > You could also just use a Longitude correction wedge if you only wanted to > correct for Longitude. > > When writing instructions. Please also include people who live in the > southern hemisphere, we do also have sundials. > > Do I have this correct? > > Roderick. > > On 3/04/2023 9:24 am, Steve Lelievre wrote: > > Jack, > > Try out my calculator! You can specify a time zone meridian for the dial > at its original location, or at its new location, or both. If there is an > effective longitude change, it'll tell you how to position (twist) the dial > on the wedge and how to orient the wedge itself, turning it away (rotating > it ) from the meridian line. > > Steve > > > On 2023-04-02 3:59 p.m., Jack Aubert wrote: > > I thought about this briefly. I had always thought that the purpose of > the shim or wedge adjustment was to tip the dial north or south so that > dial is at the latitude it was originally designed for. If the original > dial has a built-in longitude correction, that could also be factored into > a wedge which would have both a north-south and east-west axis. But a > wedge would not work if it moved the gnomon out of alignment with the with > the rotation of the earth (or the celestial sphere). I think a > longitudinal adjustment would only work if he original dial had a time-zone > offset included by rotating the hour lines with respect to the origin of > the gnomon. > > > > Does this make sense? It sounds like a good project for a 3-D printer. > > > > Jack > > > > *From:* sundial > *On Behalf Of *Steve Lelievre > *Sent:* Sunday, April 2, 2023 5:16 PM > *To:* Michael Ossipoff > *Cc:* Sundial List > *Subject:* Re: Adjusting dial to new location > > > > Michael, > > Yes, I recognize that to get Mean Time involves Equation of Time > adjustment and that Equation of Longitude can be handled there to give > Standard Time (or DST). > > But anyway, my inquiry was to seek an online wedge calculator. Nobody > identified one and a week seemed an adequate wait for responses, so I've > just written one. Anyone who's interested, please see > > > https://sundials.org/index.php/teachers-corner/sundial-construction/367-easy-dial-adjustment-for-your-latitude > > Cheers, > > Steve > > > > On 2023-04-02 1:41 p.m., Michael Ossipoff wrote: > > I just want to mention that the shim under the north or south edge of the > dial is only for latitude. Longitude is corrected-for by changing the > constant term of the Sundial-Time to Clock-Time conversion. > > > > But usually Sundial-Time, Local True Solar Time, is what I’d want from a > sundial. > > > > On Sun, Mar 26, 2023 at 14:30 Steve Lelievre < > steve.lelievre.can...@gmail.com> wrote: > > Hi, > > Can anyone point me to an existing online calculator for making a wedge > to adjust a horizontal dial to a new latitude and longitude? > > I am not asking for an explanation of how to do the calculation; I just > want to be able to point people to a calculator that has already been > proved on the internet. It should use the original location (latitude > and longitude) and the new location to calculate the angle of slope of > the wedge and the required rotation from the meridian. > > Many thanks, > > Steve > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > ---https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
...& thank you for doing so, because online calculators & dial-printing programs make sundials readily accessible to everyone. On Sun, Apr 2, 2023 at 5:15 PM Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > Michael, > > Yes, I recognize that to get Mean Time involves Equation of Time > adjustment and that Equation of Longitude can be handled there to give > Standard Time (or DST). > > But anyway, my inquiry was to seek an online wedge calculator. Nobody > identified one and a week seemed an adequate wait for responses, so I've > just written one. Anyone who's interested, please see > > > https://sundials.org/index.php/teachers-corner/sundial-construction/367-easy-dial-adjustment-for-your-latitude > > Cheers, > > Steve > > On 2023-04-02 1:41 p.m., Michael Ossipoff wrote: > > I just want to mention that the shim under the north or south edge of the > dial is only for latitude. Longitude is corrected-for by changing the > constant term of the Sundial-Time to Clock-Time conversion. > > But usually Sundial-Time, Local True Solar Time, is what I’d want from a > sundial. > > On Sun, Mar 26, 2023 at 14:30 Steve Lelievre < > steve.lelievre.can...@gmail.com> wrote: > >> Hi, >> >> Can anyone point me to an existing online calculator for making a wedge >> to adjust a horizontal dial to a new latitude and longitude? >> >> I am not asking for an explanation of how to do the calculation; I just >> want to be able to point people to a calculator that has already been >> proved on the internet. It should use the original location (latitude >> and longitude) and the new location to calculate the angle of slope of >> the wedge and the required rotation from the meridian. >> >> Many thanks, >> >> Steve >> >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Adjusting dial to new location
I just want to mention that the shim under the north or south edge of the dial is only for latitude. Longitude is corrected-for by changing the constant term of the Sundial-Time to Clock-Time conversion. But usually Sundial-Time, Local True Solar Time, is what I’d want from a sundial. On Sun, Mar 26, 2023 at 14:30 Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > Hi, > > Can anyone point me to an existing online calculator for making a wedge > to adjust a horizontal dial to a new latitude and longitude? > > I am not asking for an explanation of how to do the calculation; I just > want to be able to point people to a calculator that has already been > proved on the internet. It should use the original location (latitude > and longitude) and the new location to calculate the angle of slope of > the wedge and the required rotation from the meridian. > > Many thanks, > > Steve > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Fwd: equation of time on Earth
-- Forwarded message - From: Michael Ossipoff Date: Thu, Feb 16, 2023 at 14:12 Subject: Re: equation of time on Earth To: Kevin Karney Yes, French hours (Local True Solar Time), Babylonian hours, Italian hours & can be gotten from a sundial directly, without referring to an EoT table, & unaffected by precession of the equinoxes. I claim that nowadays sundials are of interest for Local True Solar Time anyway. EoT is more likely to be used (along with longitude-correction) to get Local True Solar Time from a clock or watch. The obliquity is constantly changing, & that will eventually put some kinds of sundials off, & those will have to be remade. Altitude Dials, & Azimuth Dials, such as the Analemmatic-Dial, use Solar-declination, which will vary with obliquely. But sundials that directly measure Solar hour-angle won’t be affected. Those include the flat-dials, including the Horizontal-Dial. …& the Equatorial-Dial, & the dials whose measuring-scale is along a band, ring or cylinder that measures around a line parallel to the Earth’s axis (I believe that those are all often called Equatorial-Dials). On Wed, Feb 15, 2023 at 15:48 Kevin Karney via sundial wrote: > Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die > eigentliche Nachricht steht dadurch in einem Anhang. > > This message was wrapped to be DMARC compliant. The actual message > text is therefore in an attachment. > > > -- Forwarded message -- > From: Kevin Karney > To: Sundial > Cc: > Bcc: > Date: Wed, 15 Feb 2023 23:47:58 + > Subject: Re: equation of time on Earth > Hi Fabio, > > I found interesting how the eot changes over the millennia and I concluded > that not all sundial time systems will survive. > > See below... > > And of course sundials will survive - just differently. The 'Clock of the > Long Now’ (which is designed to last 10,000 years) has a 3-D cam encoding > the EoT. When the sun is shining at noon, the clock will read the Sun’s > presence through an aperture, this connects thermally to the 3-D cam (see > below), which will re-set the clock to mean time. Mind-blowing project! See > https://longnow.org/clock/ > > Best wishes > Kevin > Kevin Karney > Freedom Cottage, Llandogo, > Monmouth, NP25 4TP, Wales, UK > 51°44’44” N 2°41’5” W > > > > On 14 Feb 2023, at 17:12, Fabio Savian > wrote: > > Hi all > > a couple of weeks ago I sent you news about a new app (on Sundial Atlas, > app 53) to get the equation of time of Mars. > I haven't heard of any spaceships leaving so I thought you might be > interested in the one for terrestrial resident as well :-) > > There is no shortage of software to draw eot but this new app (app 29, > www.sundialatlas.net/atlas.php?ori=29) can draw the analemma starting > from the orbital parameters of the Earth: > - eccentricity of the orbit > - inclination of the ecliptic > - longitude of the perihelion > > The app doesn't calculate these parameters but you can digit any values to > get the resulting analemma. > I found a web page of NASA (Goddard Institute for Space Studies) where you > can get the Earth's orbital parameters for the past or for the future: > https://data.giss.nasa.gov/modelE/ar5plots/srorbpar.html > > I found interesting how the eot changes over the millennia and I concluded > that not all sundial time systems will survive. > Some sundials could become archaeological finds in a few centuries just as > we look at those of centuries, or millennia ago and the understandable time > systems in the future are: temporary, Babylonians, Italians and local Sun > time. > Not the analemma because eot changes over the millennia. > Not time-zone Sun time because the conventions change over the centuries. > Not mean time because leap seconds may be not updated over the decades. > > Watching your wrist watch could become a goofy experience, one hopes to be > able to look at a sundial and know the local Sun time. > Also a Martian. > > ciao Fabio > > PS in the app 29 you can also enter parameters of other planets. > Remember that the longitude of the perihelion is a local reference, ie it > is measured from the vernal point of the planet's orbit. > > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: No more leap seconds!
I'd rather keep the leap-second. The fluctuation that it brings to clock-time only has a 1-second peak-to-peak amplitude. That's completely insignificant to dialists. & also entirely insignificant for such things as Sunrise, Sunset, Civil-Twilight & Nautical Twilight, where a cloud or a little mist can change the illumination a lot more than a few seconds of time. If they switch to leap-minutes, then we'll have to deal with a 3rd non-negligible component to the difference between clock-time & True-Solar Time. Now it's the longitude-correction & the EqT. But when they switch from leap-seconds to leap-minute, there'll be a 3rd non-negligible component: The component resulting from the long-accumulated drift or the abrupt 1-minute correction. Though of course the leap-second deals with variations in the day-length,I've heard (but not verified) that actually most of what the leap-seconds are doing is correcting for the fact that our average day-length differs from what it was in the early 19th century, when it was the basis of the official precise-timekeeping second. Since that day, our diurnal-astronomical second (1/86,400 of a mean-solar day) has changed enough that the leap-second is needed to compensate for the amount by which the diurnal-astronomical second has changed since the timekeeping-second standard was set in the early 19th century. The scientists might have very good reasons why leap-minutes would work better for them. But not for dialists or people interested in the time of Sunrise, Sunset, Civil-Twilight & Nautical-Twilight. On Thu, Nov 24, 2022 at 4:54 AM fabio.sav...@nonvedolora.it < fabio.sav...@nonvedolora.it> wrote: > Dear all, I have never commented on this topic, I do it now with a > proposal. > > - The leap second takes into account a sort of 'noise', unpredictable > before, for small variations in the speed of the Earth's rotation. > Anyway, over the millennia this speed will decrease, so the leap second is > not enough but the 'physical' second will deviate from the 'astronomical' > one. > The physical one is necessary to measure the astronomical one and they are > two different things despite the attempts of recent centuries to make them > equivalent > > - Martian days have a different second, residents will use the physical > second as unit of measurement for their scientific instrument but they will > want to live a 24-hour day (in any case full hours) with an astronomical > second significantly different from the physical one. > > - At the end of the 18th century the meter was calibrated as 1/1 of > the distance between the equator and the pole, it was later found that the > measurement is a few kilometers more and also changes from one meridian to > another, not to mention the equator. > This did not change the unit of measurement and did not impose a wrong > measurement of the Earth. It is accepted that the meter has an autonomous > definition distinct from the geographic measurements of the planet. > > In my opinion the problem is in the name: the 'second' is a name that > derives from a fraction of the day while the physical second is a unit of > measurement that is still unnamed. > If the physical second had a definition, it would help put an end once and > for all between the demands of scientific measurement and the rhythm of a > planet's days. > The gnomonists are the most focused community on the history of time for > which I am launching a proposal: > help the scientific world to find a definition for the physical second, > giving it a separate identity from the local astronomical second (Earth, > Mars, etc.). > This forum could be the place to put forward some shared proposal and > start using it. > It does not matter if the scientific community wants to change it, it > would still be a success to have established that the physical second has a > different name and identity from our dear old terrestrial second. That of > clocks and sundials, and of our terrestrial life. > > Long live the second, ciao Fabio > > > Il 21/11/2022 17:39, Steve Lelievre ha scritto: > > > Ah, the joys of Listservs and email software. My participation sometimes > gets of of step too: occasionally, original posts reach me after other > people's replies. > > Perhaps it wouldn't be a problem if all the world's computers were exactly > synchronized... perhaps they could use atomic clocks for that ;-) > > Cheers, > > Steve > > > On 2022-11-21 12:04 a.m., John Pickard wrote: > > Sorry Steve, > > I sent my post before seeing yours. > > -- > Cheers, John. > > Dr John Pickard. > > > > ---https://lists.uni-koeln.de/mailman/listinfo/sundial > > -- > Fabio savianfabio.sav...@nonvedolora.itwww.nonvedolora.eu > Paderno Dugnano, Milano, Italy > 45° 34' 9'' N, 9° 9' 54'' E, UTC +1 (DST +2) > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
Re: Metal gnomons
What’s wrong with brass changing its color with weathering? Isn’t that part of the appeal of brass? On Sat, Apr 30, 2022 at 8:56 AM Dan-George Uza wrote: > Hi, > > Iron rusts and brass changes color, but what about different metals used > as gnomons, pros & cons? > > What would be the appropriate choice of material for a replica of an 18th > century cubical multiple sundial? It should ideally come as an industrial > sheet ready for cutting and also not stain the limestone face. > > I like the metal in the attached photo (Sundial Atlas CH 000247). Do you > know what it is? > > Thanks, > > Dan Uza > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Typo correction in most recent post
# 5, in my most recent post, should say: . To determine the hour-angle of the mean-Sun: . 1. Convert the minutes in the LMT to a fraction of an hour. . 2. Subtract 12 hours from the LMT, or add 12 hours to the LMT…whichever gives a number between 0 & 24. . 3. Multiply the result by 15. --- The reason for this correction is that I’d forgotten that hour-angle & time are reckoned from different starting-points: Hour angle is measured from the meridian (in the south)… …& time is measured from the anti-meridian. i.e. from when the Sun or the mean-Sun is at the anti-meridian. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
EqT estimate without knowing when Eqt was zero
(I’d post this as a “reply” to my existing topic, but that thread doesn’t show up in my display, & so it’s necessary to post this as a new topic.) . Yesterday I described a way of estimating EqT, which depended on the fact that the EqT is zero on some known day. But EqT can be also estimated without knowing when it is zero. …by use of Sidereal Time. . First in summary, & then with details for the summarized elements: . For some given time of day, in Standard-Time, convert it to local mean time, by applying your longitude-correction. . 1. Determine ecliptic-longitude as before. Even if not reliably, estimate it as well as possible for a particular time of day. (Each half-day in error for when an ecliptic-month starts only makes a 2 minute error in the EqT estimate.) . 2. As before, use Spherical Trigonometry’s Cosine Formula to determine the Sun’s R.A., in degrees, from its ecliptic-longitude. . 3. Determine the Sidereal Time (…the hour-angle of the Vernal-Equinox. Hour-angle is measured westward around the Earth’s axis, from the meridian, in the south.) . 4. Subtract the Sun’s R.A. from 360, & add the result to the Sidereal Time in degrees. . 5. From the local mean time, determine the hour-angle of the mean Sun, in degrees. . 6. Subtract the hour-angle of the Sun from the hour-angle of the mean-Sun. Multiply by 4, & that gives EqT. . Details, where needed: . 2. The Spherical-Trigonometry Cosine Formula, for ecliptic-longitude & R.A: . To get the Sun’s R.A.: . Multiply the tangent of its ecliptic-longitude by the cosine of the obliquity, & then take the inverse tangent of the result. . 3. Sidereal-Time: . Sidereal Time, like Mean Time advances uniformly. . It takes us roughly 365.25 days to orbit the Sun. That’s slightly longer than a mean tropical year. That’s because the equinoxes come about 1/72 of a degree to meet us partway, making our tropical year about 20 minutes shorter than the sidereal year. (Of course those year-lengths really depend on from what part of our orbit they’re measured.) . Because of the Sun’s apparent eastward movement with respect to the fixed stars, due to our orbital motion around it, in a sidereal year the fixed stars will have been perceived to go around us one more time than the Sun has. In a sidereal year, the stars will have gained 360 degrees over the mean Sun. . So, in a day they’ll gain about (360/365.25) degrees, or about .9856 degree. . On the day of the Autumnal Equinox, if it occurs at Local Mean Time (LMT) midnight, the Vernal Equinox will be on the meridian at midnight, because the equinoxes are opposite. . So, how many days since the Autumnal Equinox, & how many hours since midnight? Each hour since midnight advances the Vernal-Equinox 15 degrees westward. Each day since the Autumnal Equinox avances the Vernal Equinox about .9856 degree westward. . Of course if the Autumnal Equinox occurred some hours later than midnight LMT, then at any later date & time the Vernal Equinox’s hour-angle will be advanced 15 degrees less for each of those hours later. …& of course the opposite if it’s earlier. . In that way, you can determine hour-angle of the Vernal Equinox at any time & date. . 5. Hour angle of the local mean sun: . It’s 15 degrees for every hour past noon local mean time. , I haven’t tried this method yet, but its error is probably about the same as the other method I described. . I guess most of the error comes from the approximation of the Solar Ecliptic Longitude via the Indian National Calendar. . That calendar seeks to make each of its ecliptic-months start as close as possible to the actual astronomical ecliptic-month, & so I wouldn’t expect large cumulative errors to accumulate. . The length of an Indian National Calendar ecliptic-month could be off by up to half a day at most. Each half-day of error makes a 2 minute EqT error. But the calendar’s errors are intended to not accumulate. As I described for October 29th, the EqT error was only 1 minute. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Calculation & Estimation of Solar ecliptic-longitude & EqT
I forgot to mention that the amount by which the mean sun gains on the actual sun in R.A. is eastward, in the opposite direction to the Sun's diurnal motion. ...& so, the amount by which the mean Sun gains on the actual Sun in hour-angle. is the negative of the amount by which it gains on the actual Sun in R.A. So when the mean Sun's R.A. gain over the actual Sun during the period of interest is determined, & multiplied by 4, you must change the sign of that difference to get the EqT. On Sat, Oct 29, 2022 at 8:48 PM Michael Ossipoff wrote: > There was something posted recently about how to calculate the Solar > ecliptic-longitude, & thereby the Equation of Time (EqT). > > . > > (I should emphasize, that, when the Solar ecliptic-longitude is determined > as described below, of course the Solar declination can be gotten from it > by the method that we discussed earlier.) > > . > > It used a formula derived by solving our Solar orbit. > > . > > With matters like that, it’s of interest how the formulas are derived. > > . > > I once solved the orbital problem. It wasn’t for planetary-orbits. I > wanted to find out how far the fastest rifle bullet (4110 fps, from > something I’d read 20 years previous) could go, on the moon. > > . > > If the ground were flat, with uniform gravitational-field, I get about 600 > miles. But, for such a long range, those assumptions aren’t good enough. > It’s necessary to do it as an orbital problem. …an orbit about the > moon’s center, that intersects the moon’s surface. > > . > > (The answer that I got was just a bit more than 800 miles. It might have > been about 820 miles.) > > . > > For me, by far the most straightforward solution-method was by > conservation-laws. …as opposed to the solution-method that uses > dynamics. > > . > > Well one of the conservation-laws—conservation of angular-momentum, is > proved via dynamics. By far the simplest & most straightforward way to do > that is in Lagrangian dynamics. > > . > > The conservation-laws solution involves an integral that can be solved in > closed form. (Numerical-integration isn’t necessary.) > > . > > And, as is so often the case, it’s one of those integrations that requires > trial-&-error to find the Integrand’s antiderivative. > > . > > There are several methods for converting the problem of integrating one > function, to a problem of integrating a different one. So you apply > whichever of those methods seems most promising, & if it seems to give you > a new integration problem that looks simpler or more promising, then you > apply one of the conversion methods to that new integral…& keep doing so > till it leads to an expression whose integral is known. > > . > > So the integration involved a bit of trial & error, but was solvable in > closed form. (…as opposed to requiring a numerical approximation.) > > . > > But, if you’re on a desert island, & need the EqT for > position-determination, or for some reason you need mean time or standard > time from your sundial, then to use a solution of the Earth’s orbit, you’d > have to: > > . > > 1. Solve our orbit to derive the formulas. > > . > > OR > > . > > 2. Have a piece of paper on which the formula is written > > . > > OR > > . > > 3. Have been solving orbits so regularly & recently that you don’t need > to look up the needed formulas. > > . > > And another problem is that you’d need the initial conditions at some > recent epoch. That too would have to be looked-up. …again, unless > you’ve been doing the problem so much lately that you know the > initial-conditions. > > . > > ….&, if you’re going to carry around a piece of paper with the > orbital-solution formula & the initial-conditions…well then, why not just > carry a piece of paper with the EqT & Solar declination for each day of the > current year (…& maybe the next few years if you might be on your desert > island or at sea for a few years)? > > . > > So it would be desirable to have an easier approximation for the EqT. > > . > > I’ll suggest one. > > . > > The month-lengths of the ecliptic-month approximations in the Indian > National Calendar can give you an estimate of the Solar ecliptic-longitude > for any day, if you know the date of the nearest equinox (or even roughly > if not exactly). > > . > > Start with a day known to have an EqT of zero. September 1st & Christmas > are such days. > > . > > The Indian National Calendar has 30-day & 31-day months. > > . > > Taurus thru Virgo have 31 days.
Calculation & Estimation of Solar ecliptic-longitude & EqT
There was something posted recently about how to calculate the Solar ecliptic-longitude, & thereby the Equation of Time (EqT). . (I should emphasize, that, when the Solar ecliptic-longitude is determined as described below, of course the Solar declination can be gotten from it by the method that we discussed earlier.) . It used a formula derived by solving our Solar orbit. . With matters like that, it’s of interest how the formulas are derived. . I once solved the orbital problem. It wasn’t for planetary-orbits. I wanted to find out how far the fastest rifle bullet (4110 fps, from something I’d read 20 years previous) could go, on the moon. . If the ground were flat, with uniform gravitational-field, I get about 600 miles. But, for such a long range, those assumptions aren’t good enough. It’s necessary to do it as an orbital problem. …an orbit about the moon’s center, that intersects the moon’s surface. . (The answer that I got was just a bit more than 800 miles. It might have been about 820 miles.) . For me, by far the most straightforward solution-method was by conservation-laws. …as opposed to the solution-method that uses dynamics. . Well one of the conservation-laws—conservation of angular-momentum, is proved via dynamics. By far the simplest & most straightforward way to do that is in Lagrangian dynamics. . The conservation-laws solution involves an integral that can be solved in closed form. (Numerical-integration isn’t necessary.) . And, as is so often the case, it’s one of those integrations that requires trial-&-error to find the Integrand’s antiderivative. . There are several methods for converting the problem of integrating one function, to a problem of integrating a different one. So you apply whichever of those methods seems most promising, & if it seems to give you a new integration problem that looks simpler or more promising, then you apply one of the conversion methods to that new integral…& keep doing so till it leads to an expression whose integral is known. . So the integration involved a bit of trial & error, but was solvable in closed form. (…as opposed to requiring a numerical approximation.) . But, if you’re on a desert island, & need the EqT for position-determination, or for some reason you need mean time or standard time from your sundial, then to use a solution of the Earth’s orbit, you’d have to: . 1. Solve our orbit to derive the formulas. . OR . 2. Have a piece of paper on which the formula is written . OR . 3. Have been solving orbits so regularly & recently that you don’t need to look up the needed formulas. . And another problem is that you’d need the initial conditions at some recent epoch. That too would have to be looked-up. …again, unless you’ve been doing the problem so much lately that you know the initial-conditions. . ….&, if you’re going to carry around a piece of paper with the orbital-solution formula & the initial-conditions…well then, why not just carry a piece of paper with the EqT & Solar declination for each day of the current year (…& maybe the next few years if you might be on your desert island or at sea for a few years)? . So it would be desirable to have an easier approximation for the EqT. . I’ll suggest one. . The month-lengths of the ecliptic-month approximations in the Indian National Calendar can give you an estimate of the Solar ecliptic-longitude for any day, if you know the date of the nearest equinox (or even roughly if not exactly). . Start with a day known to have an EqT of zero. September 1st & Christmas are such days. . The Indian National Calendar has 30-day & 31-day months. . Taurus thru Virgo have 31 days. The other months have 30 days. . Taurus starts in April. Virgo starts in August. . So, Taurus & Virgo are the ecliptic months that start in a month that starts with “A”. . In a 31 day month, the average motion rate along the ecliptic is 30/31 degrees per day. . In a 30 day month, the average motion rate along the ecliptic is 1 degree per day. . Start with a day known to have an EqT of zero. September 1st & Christmas are two such days. . (There are four of them, but you might not need all four.) . So, based on that, determine the Solar ecliptic longitude on (say) September 1st, & on the date whose EqT you want. . For each of those two EqT values, use spherical-trigonometry’s Cosine Formula to determine the equatorial-longitude--the Right-Ascencion (R.A.), in degrees--that corresponds to that ecliptic-longitude for motion along the ecliptic. . Subtract the two R.A. values to find out how much the actua Sun increases its R.A. between September 1st & the date whose EqT you want. . Next you want to know how far the mean-Sun moves in R.A. during that same period, from September 1st, to the date whose EqT you want. . Well, it takes 1 year for the Sun to go 360 degrees around the ecliptic, to return to some initial point. That’s called a tropical-year.
Re: How to turn ecliptic longitude into solar declination?
Okay, that’s good to hear. …& thanks clearing it up. On Sun, Oct 16, 2022 at 3:54 PM Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > Michael, > > On 2022-10-16 1:40 p.m., Michael Ossipoff wrote: > > Thank you for mentioning that I answered Steve's question. > > ...something not acknowledged by Steve for some reason. > > > Please be assured that no slight was intended. Thank you for taking the > time to reply to my question. > > I did not acknowledge your response because I had not seen it. My email > software treated your messages as spam so I didn't see them until > Frank's message prompted me to check the junk folder. Just as soon as I > figure out the applicable setting, I'll change it. > > Steve > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: How to turn ecliptic longitude into solar declination?
Frank-- Thank you for mentioning that I answered Steve's question. ...something not acknowledged by Steve for some reason. I didn't notice that when I first read your post. Thanks for setting the record straight ! So, to the list I just want to clarify that, when Steve asked how to determine declination from ecliptic-longitude, I was the first to answer his question, when I gave the following instruction: "Multiply the sine of the ecliptic-longitude by the sine of the obliquity, & then take the inverse-sine of the result." October 16th --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: How to turn ecliptic longitude into solar declination?
[quote] At the moment we are in Vintagarious, the first month, and you will see that each day has the symbol for Aries. [/quote] Then you have an error, because Vendemiaire doesn't roughly approximate Aries. Vendemiaire roughly approximates Libra. As for the nature of the French Republican Calendar's rough approximation of the ecliptic-months, due to its piling up its excess 5 or 6 says all at the end of the year, IL amply covered that in earlier posts. The Indian National Calendar does a much better job, when it gives 31 days to Taurus thru Virgo. The Indian National Calendar isn't a fixed calendar. No blank days & no periodic-error-increase due to a leapweek. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: How to turn ecliptic longitude into solar declination?
I emphasize that saying that each third of an ecliptic-month is 10 degrees is not an approximation. An ecliptic-month is defined as exactly 1/3 of an astronomical- quarter…1/3 by ecliptic-longitude, not by time or days. An astronomical-quarter is the ecliptic interval between a solstice & an equinox…90 degrees along the ecliptic. On Fri, Oct 14, 2022 at 11:33 PM Michael Ossipoff wrote: > BTW, I like sundials that tell the ecliptic-months, Aries thru Pisces. > > …for which one would need the Solar declinations for the beginning of each > ecliptic-month, & preferably also for some fractions of each > ecliptic-month, such as 1/3 & 2/3. > > On Fri, Oct 14, 2022 at 10:16 PM Michael Ossipoff > wrote: > >> >> >> ------ Forwarded message - >> From: Michael Ossipoff >> Date: Fri, Oct 14, 2022 at 10:16 PM >> Subject: Re: How to turn ecliptic longitude into solar declination? >> To: Steve Lelievre >> >> >> >> >> Or you could just use the ecliptic longitude, reckoned as usual from the >> Vernal Equinox…multiply its sine by the sine of the obliquely & take the >> inverse sine of the result. >> >> I’d suggested that other way because there are some spherical >> trigonometry formulas that require an argument between 0 & 90 degrees. >> >> …but that isn’t one of them. >> >>> >>> >>> On Fri, Oct 14, 2022 at 6:49 PM Michael Ossipoff >>> wrote: >>> >>>> Multiply the sine of ecliptic longitude (reckoned forward or backwards >>>> from the nearest equinox) by the sine of 23.438 or whatever the current >>>> obliquity’s exact value is). >>>> >>>> Take the inverse sine of the result. >>>> >>>> On Fri, Oct 14, 2022 at 4:57 PM Steve Lelievre < >>>> steve.lelievre.can...@gmail.com> wrote: >>>> >>>>> >>> Of course you’ll know when the declination is negative or positive, so >>> mark it accordingly. >>> >>> >>> >>> Hi, >>>>> >>>>> For a little project I did today, I needed the day's solar declination >>>>> for the start, one third gone, and two-thirds gone, of each zodiacal >>>>> month (i.e. approximately the 1st, 11th and 21st days of the zodiacal >>>>> months). >>>>> >>>>> I treated each of the required dates as a multiple of 10 degrees of >>>>> ecliptic longitude, took the sine and multiplied it by 23.44 (for >>>>> solstitial solar declination). At first glance, the calculation seems >>>>> to >>>>> have produced results that are adequate for my purposes, but I've got >>>>> a >>>>> suspicion that it's not quite right (because Earth's orbit is an >>>>> ellipse, velocity varies, etc.) >>>>> >>>>> My questions: How good or bad was my approximation? Is there a better >>>>> approximation/empirical formula, short of doing a complex calculation? >>>>> >>>>> Cheers, >>>>> >>>>> Steve >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> --- >>>>> https://lists.uni-koeln.de/mailman/listinfo/sundial >>>>> >>>>> --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: How to turn ecliptic longitude into solar declination?
BTW, I like sundials that tell the ecliptic-months, Aries thru Pisces. …for which one would need the Solar declinations for the beginning of each ecliptic-month, & preferably also for some fractions of each ecliptic-month, such as 1/3 & 2/3. On Fri, Oct 14, 2022 at 10:16 PM Michael Ossipoff wrote: > > > -- Forwarded message ----- > From: Michael Ossipoff > Date: Fri, Oct 14, 2022 at 10:16 PM > Subject: Re: How to turn ecliptic longitude into solar declination? > To: Steve Lelievre > > > > > Or you could just use the ecliptic longitude, reckoned as usual from the > Vernal Equinox…multiply its sine by the sine of the obliquely & take the > inverse sine of the result. > > I’d suggested that other way because there are some spherical trigonometry > formulas that require an argument between 0 & 90 degrees. > > …but that isn’t one of them. > >> >> >> On Fri, Oct 14, 2022 at 6:49 PM Michael Ossipoff >> wrote: >> >>> Multiply the sine of ecliptic longitude (reckoned forward or backwards >>> from the nearest equinox) by the sine of 23.438 or whatever the current >>> obliquity’s exact value is). >>> >>> Take the inverse sine of the result. >>> >>> On Fri, Oct 14, 2022 at 4:57 PM Steve Lelievre < >>> steve.lelievre.can...@gmail.com> wrote: >>> >>>> >> Of course you’ll know when the declination is negative or positive, so >> mark it accordingly. >> >> >> >> Hi, >>>> >>>> For a little project I did today, I needed the day's solar declination >>>> for the start, one third gone, and two-thirds gone, of each zodiacal >>>> month (i.e. approximately the 1st, 11th and 21st days of the zodiacal >>>> months). >>>> >>>> I treated each of the required dates as a multiple of 10 degrees of >>>> ecliptic longitude, took the sine and multiplied it by 23.44 (for >>>> solstitial solar declination). At first glance, the calculation seems >>>> to >>>> have produced results that are adequate for my purposes, but I've got a >>>> suspicion that it's not quite right (because Earth's orbit is an >>>> ellipse, velocity varies, etc.) >>>> >>>> My questions: How good or bad was my approximation? Is there a better >>>> approximation/empirical formula, short of doing a complex calculation? >>>> >>>> Cheers, >>>> >>>> Steve >>>> >>>> >>>> >>>> >>>> >>>> --- >>>> https://lists.uni-koeln.de/mailman/listinfo/sundial >>>> >>>> --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Fwd: How to turn ecliptic longitude into solar declination?
-- Forwarded message - From: Michael Ossipoff Date: Fri, Oct 14, 2022 at 10:16 PM Subject: Re: How to turn ecliptic longitude into solar declination? To: Steve Lelievre Or you could just use the ecliptic longitude, reckoned as usual from the Vernal Equinox…multiply its sine by the sine of the obliquely & take the inverse sine of the result. I’d suggested that other way because there are some spherical trigonometry formulas that require an argument between 0 & 90 degrees. …but that isn’t one of them. > > > On Fri, Oct 14, 2022 at 6:49 PM Michael Ossipoff > wrote: > >> Multiply the sine of ecliptic longitude (reckoned forward or backwards >> from the nearest equinox) by the sine of 23.438 or whatever the current >> obliquity’s exact value is). >> >> Take the inverse sine of the result. >> >> On Fri, Oct 14, 2022 at 4:57 PM Steve Lelievre < >> steve.lelievre.can...@gmail.com> wrote: >> >>> > Of course you’ll know when the declination is negative or positive, so > mark it accordingly. > > > > Hi, >>> >>> For a little project I did today, I needed the day's solar declination >>> for the start, one third gone, and two-thirds gone, of each zodiacal >>> month (i.e. approximately the 1st, 11th and 21st days of the zodiacal >>> months). >>> >>> I treated each of the required dates as a multiple of 10 degrees of >>> ecliptic longitude, took the sine and multiplied it by 23.44 (for >>> solstitial solar declination). At first glance, the calculation seems to >>> have produced results that are adequate for my purposes, but I've got a >>> suspicion that it's not quite right (because Earth's orbit is an >>> ellipse, velocity varies, etc.) >>> >>> My questions: How good or bad was my approximation? Is there a better >>> approximation/empirical formula, short of doing a complex calculation? >>> >>> Cheers, >>> >>> Steve >>> >>> >>> >>> >>> >>> --- >>> https://lists.uni-koeln.de/mailman/listinfo/sundial >>> >>> --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: How to turn ecliptic longitude into solar declination?
Multiply the sine of ecliptic longitude (reckoned forward or backwards from the nearest equinox) by the sine of 23.438 or whatever the current obliquity’s exact value is). Take the inverse sine of the result. On Fri, Oct 14, 2022 at 4:57 PM Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > Hi, > > For a little project I did today, I needed the day's solar declination > for the start, one third gone, and two-thirds gone, of each zodiacal > month (i.e. approximately the 1st, 11th and 21st days of the zodiacal > months). > > I treated each of the required dates as a multiple of 10 degrees of > ecliptic longitude, took the sine and multiplied it by 23.44 (for > solstitial solar declination). At first glance, the calculation seems to > have produced results that are adequate for my purposes, but I've got a > suspicion that it's not quite right (because Earth's orbit is an > ellipse, velocity varies, etc.) > > My questions: How good or bad was my approximation? Is there a better > approximation/empirical formula, short of doing a complex calculation? > > Cheers, > > Steve > > > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Republican Calendar, Year 231
Oops!! At the time of writing, it's still only September 29th in Greenwich. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Suggested Improvements to Universal Celestial Calendar
Calendar-reform was seriously considered by the League of Nations, & maybe even by the U.N. for a while, but nowadays, alternative calendar-proposals can only be regarded as an artform. . But even as an artform, for any popularity, some design-consensus & traditional-compliance is desirable. . As I mentioned, Gregorius assembled a team of astronomers & mathematicians. …as did Julius Caesar & the French Republicans. Calendar design & proposal isn’t a one-man project. . If you’ve looked at the UCC website, you might feel that UCC still needs some work. There’s nothing wrong with that, because Calendars should be collaborative. . The significant thing about UCC is that it’s a beautiful concept, & I don’t know of any proposal like it. …& it has some popularity, traction & momentum. . I’ll list some of its issues, & address them. . But first I want to emphasize that, though I don’t like blank-days, nearly all new calendar proposals are for fixed calendars, and most of those use blank days. I don’t suggest getting rid of UCC’s blank-days of 10-day week, even though those attributes would destroy its chances as a serious proposal, if calendar-reform were actually being considered. . Elizabeth Achellis proposed her World Calendar for a number of decades. The League of Nations was seriously considering calendar-reform, & her proposal might very well have been endorsed by the League of Nations, if only she’d relented about the blank-days. . There was a compromise offer, from at least one of the world’s major religions, to accept the World Calendar, if its blank-days were replaced by a leapweek, as the way of achieving a fixed calendar. Achellis rejected that compromise, thereby throwing away the World Calendar’s chance for acceptance. . Though blank-days, a 10-day week, & a changed year-numbering would be rejected by the world’s religions, and would be inconsiderate of the billions of people who belong to those religions, & I wouldn’t want them in a serious proposal--I don’t suggest removing those things from UCC, because it’s only an artform, & because FRC has those attributes anyway, & because there’s a limit to how much one can change a proposal. . But here are some changeable issues about UCC. . 1. The wheel of the year is always drawn clockwise…probably because that’s how the Sun goes around the sky in the Northern-Hemisphere. Yes, the Sun’s movement on the ecliptic is counterclockwise, as viewed in the Northern-Hemisphere. UCC’s wheel of the year is drawn counterclockwise. I suggest that it should be drawn clockwise, to bring it into conformity with the long tradition about the wheel of the year. . 2. The yearstart target-day of UCC is the first whole day after the Vernal Equinox. That means that the calendar’s oscillation isn’t about the Vernal Equinox, but rather is about a time after the Vernal Equinox. . So change the target yearstart time to the Vernal Equinox itself. . Start the year on the day that starts closest to the Vernal Equinox (or to an approximation thereof). . 3. For UCC, a leapyear-schedule is proposed. It’s motivation isn’t transparent, & it looks arbitrary. If you want to use a new arithmetical yearstart rule, then it would be better to use the simple, obvious, natural & transparent one that I proposed for the North Solstice Ecliptic-Months Calendar. …except, of course for the Vernal-Equinox tropical year. . Such a rule would also have the absolute least possible maximum-periodic-displacement, and an obvious & low unidirectional drift-rate….lower than the one stated for the UCC’s proposed rule. . 4. When proposing a new ecliptic-months calendar with blank-days, at least place them to achieve the best approximation to the actual astronomical ecliptic-months. . That means: . Give the blank-days to the ecliptic months of Taurus thru Virgo. …& give the leapday-blank-day to Aries. . 5. Drop the UCC’s novel Great-Year system of modified Precessional-Ages. By long tradition, the Precessional-Ages are the periods during which the Vernal-Equinox is in the various sidereal signs of the Zodiac. UCC should keep those traditional Ecliptic-Ages. . …instead of imposing 2000-year precessional-ages, which don’t match those of the actual sidereal signs. The current UCC diagram shows us to be at the east end of the Age of Pisces, when actually we’re at the west end of it, only about 5 degrees, or 350 years, from the Age of Aquarius. That won’t due, for wide-acceptance. . Though I like including the Apsidal-Age in addition to the Precessional-Age, I wouldn’t press for that change, because I haven’t heard any agreement on that. . 25 September . 5 SEVEN-Libra . 3rd of Wheezy . Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Publish the Universal Celestial Calendar !!
I'd like to suggest that the people who are publishing FRC consider publishing UCC as well....as an alternative-emphais Ecliptic-Months Calendar. ...a Celestial one, in addition to the Terrestrial FRC. If you google "Universal Celestial Calendar", there'll be a link to the UCC homepage. Go there. At the top of the page, click on "Blogs". At that Blogs page, Littmus Freeman's e-mail address can be found. Well why not just give that e-mail address here, for anyone interested in publishing his beautkiful Celestial Ecliptic-Months calendar:: free...@wisdomworkouts.net But explore the larger website, starting from its homepage. It's fascinating. 5 SEVEN-Libra Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Perpetual Calendar of Giovanni Antonio Amedeo Plana
It's an amazing device, especially for its time, & its mechanical-construction. I'd never heard of it till today. When you google "Giovanni Antonio Amedeo Plana, perpetual calendar, Turin", select the google link that says: " The mechanism of Plana's Calendar - IMEKO That looks like more than a magazine-article, & looks to have a more detailed description of the device. Michael Ossipoff <https://www.imeko.org/publications/tc4-Archaeo-2017/IMEKO-TC4-ARCHAEO-2017-008.pdf> On Sat, Sep 24, 2022 at 1:22 PM graham stapleton via sundial < sundial@uni-koeln.de> wrote: > Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die > eigentliche Nachricht steht dadurch in einem Anhang. > > This message was wrapped to be DMARC compliant. The actual message > text is therefore in an attachment. > > > -- Forwarded message -- > From: graham stapleton > To: "sundial@uni-koeln.de" > Cc: > Bcc: > Date: Sat, 24 Sep 2022 17:22:31 + (UTC) > Subject: Perpetual Calendar of Giovanni Antonio Amedeo Plana > While calendars are a current topic, please can anyone direct me to > detailed information about the Perpetual Calendar created by Giovanni > Antonio Amedeo Plana, located in Turin. > > I have discovered a paper: IMEKO-TC4-ARCHAEO-2017-008.pdf > <https://www.imeko.org/publications/tc4-Archaeo-2017/IMEKO-TC4-ARCHAEO-2017-008.pdf> > but > it has few details. Apparently the University of Turin team built both a > physical replica and a digital version, I have not found any references to > these. > > Graham Stapleton > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Republican Calendar, Year 231
isplaces the most tropical-year-constant ecliptic-longitude a bit away from where our orbital aphelion is. . Anyway, the UCC’s distribution of the blank-days around the year brings some ecliptic-accuracy improvement. But it would be best of all to give the blank-days to the ecliptic-months from Taurus thru Virgo. …& give the leapyear blank-day to Aries. . If it’s objeceted that that distribution wouldn’t be balanced, then I answer that it would be symmetrically balanced about our orbital aphelion. . That’s how the Indian National Calendar gives its 31st day. . Both calendars, FRC & UCC can be beautifully drawn & illustrated. . Though I don’t think there will ever be (or need be) calendar-reform, it might be desired at a Utopian-Epoch, if people want the world to start completely anew, for a complete break with the bad-old-days…including the adoption of a completely new & different calendar. . That’s what I like about alternative calendars. The Utopian-Epoch, & therefore calendar-reform, is Utopian fantasy sci-fi, but what’s wrong with that? . Actuality is over-rated. . Date for current Greenwich Time: . September 25th (Roman-Gregorian) . 1st degree of Libra (astronomical Solar ecliptic longitude—the degree of Libra that the Sun is in)] . 2 degrees into Libra (astronomical distance into Libra rounded to nearest degree) . 3rd of Vendemiaire (FRC) . 3rd of Wheezy (FRC) . 5 SEVEN-Libra (UCC) . 5th of Libra (North Solstice Ecliptic-Months Calendar) . Michael Ossipoff , (FRC is more accurate right now because its starting day is so recent.) On Wed, Sep 21, 2022 at 3:52 PM Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > On 2022-09-21 3:22 a.m., Michael Ossipoff wrote: > > Yes some of you over there like to rely on exaggeration as an attack-tactic > > I hope it's unintentional on your part, but the words "some of you over > there" hint at a prejudice that disrespects not only Frank King but also > others from his part of the world. > > Though we could call every country & city by its earliest known ancient > name, it’s a bit different with a person’s name. > > It is seems pretty evident to me that historical figures of note were > routinely referred to using the name form applicable to the language being > spoken. Indeed, the convention persists today - think of the current pope. > He signs himself as Franciscus on papal papers, but he is routinely called > Francesco in Italian, Francisco in Spanish, François in French, Francis > in English, and so on. > > As well, the idea that the Vatican would allow an unacceptable or > incorrect name form to be used on a tomb inside St. Peter’s Basilica, is > ridiculous. Yet, as Frank mentioned, the tomb uses the name Gregorio. For > confirmation, here is a clip from a photo. > > So, Frank's use of 'Gregory' is the normal practice. I'm not surprised > that he reacted in his quirky way to an unjustified comment. > > > > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Republican Calendar, Year 231
Steve: . You said: . [quote] I'm not surprised that he reacted in his quirky way to an unjustified comment. [/quote] . Oh really? Frank was using that same argumentative Internet attack-style, completely uncalled-for, in his initial post to me, before I’d said anything to him: . I quote: . [quote] Without changing ANY detail of the specification of the Gregorian Calendar (which you clearly want to keep) you follow the precedent set by your hero Pope Gregory III [/quote] . So, he was using the argumentative attack-exaggeration that I referred to, before I’d written anything to him. It was “out of the blue”, unprovoked, & uncalled-for. Right out of the starting-gate. . …& of course then he repeated the same wording, “your hero Pope Gregory III”. Evidently he was afraid that he wasn’t heard the first time. I didn’t say anything the first time, but, with the 2nd time I mentioned it. Do you think maybe if he doesn’t want to have it mentioned, then maybe he doesn’t have to do it with repetition? . And yes, I *have* encountered that before. There was something all too familiar about it. . So his unprovoked attack-language is okay, but my mentioning it is not? . You said: . [quote] On 2022-09-21 3:22 a.m., Michael Ossipoff wrote: . [quote] Yes some of you over there like to rely on exaggeration as an attack-tactic [/quote] I hope it's unintentional on your part, but the words "some of you over there" hint at a prejudice that disrespects not only Frank King but also others from his part of the world. [/quote] . I neither said nor implied nothing about everyone in any region or place. Neither did I say or imply anything about anyone other than some individuals by whom I was attacked in the manner which I referred to. . I said “some”. I didn’t generalize to any whole population anywhere. . …& I didn’t “disrespect” Frank. I merely called him on his inappropriate argumentative conduct. . There was no”prejudice”. Prejudice means prejudgement. Whom, pray tell, did I prejudge? . I referred to a particular thing that Frank had said. …& to prior experience with the same behavior. . Prejudgment means judging people you haven’t met, or people about whom you have no basis for what you’re saying, You’re straining the meaning of “prejudice”, bigtime. . No, I only made reference to past experience, but I didn’t express any judgment regarding anyone I haven’t been abused by. I was referring to the abusers that I’ve experienced, but I made no blanket judgments about anyone other than the attackers that I’ve encountered. . …& I didn’t imply that they comprise a significant or large proportion of any population. . …so where was the prejudgment by me? . About Gregorius vs Gregory: . I didn’t use the words “incorrect”, or “unacceptable”, or imply that Frank’s usage was unusual or uncommon. I merely made the uncontroversial obvious statement that Pope Gregorius didn’t call himself Gregory. The discussion was about his official actions, not about his chums called him in casual conversation. . So it’s common to call people by names other than their own (& by other languages’ equivalent names)? Fine. Whether it’s common or otherwise, I merely stated an instance of that. I said nothing about “incorrect” or “unacceptable”, & I made no statement regarding how many or how few people do that. . When Gregorius issued the order, he was acting in his official capacity as pope. He was acting as Pope Gregorius, not as Gregory or Greg. . As you yourself brought up: When Gregorius signed the document specifying the changes in the Julian Calendar, in 1582, with what name was his edict or order signed? . Whatever names he’s called by in various other milieux, settings or situations, especially outside his official capacity, or in other countries, he signed that thing as Gregorius. . Those are reasons why I made my comment. But I said only what I said, & I didn’t say “incorrect”, “unacceptable”, or anything about how many people use other names. I didn’t say what you attributed to me. . In summary, maybe it’s sometimes best to fact-check what one is saying about another person before posting it. On Wed, Sep 21, 2022 at 3:52 PM Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > On 2022-09-21 3:22 a.m., Michael Ossipoff wrote: > > Yes some of you over there like to rely on exaggeration as an attack-tactic > > I hope it's unintentional on your part, but the words "some of you over > there" hint at a prejudice that disrespects not only Frank King but also > others from his part of the world. > > Though we could call every country & city by its earliest known ancient > name, it’s a bit different with a person’s name. > > It is seems pretty evident to me that historical figures of note were > routinely referred to using the name form applicable to the l
Re: Republican Calendar, Year 231
Yes some of you over there like to rely on exaggeration as an attack-tactic, but in this instance it isn’t an exaggeration. You keep calling Gregorius a hero, but that isn’t an exaggeration. Gregorius & his astronomers saved the Julian Calendar when they restored it’s original seasonal positioning, & improved the leap year rule to keep it that way. Gregorio sounds like an Italianization. But Latin was official in the Catholic Church. He didn’t call himself Gregory. His official church name was Gregorius. Though we could call every country & city by its earliest known ancient name, it’s a bit different with a person’s name. How did he officially refer to himself? On Wed, Sep 21, 2022 at 12:33 AM Frank King wrote: > Dear Michael, > > I am most grateful to you for pointing out > an error in my message. I referred to: > > > ... your hero Pope Gregory III > > and you correctly commented: > > > I doubt that he called himself Gregory... > > Quite so, BUT you missed a MUCH more serious > error. He was neither Gregory III nor > Gregorius III. I omitted the X from XIII. > Many apologies for that. > > > His name was Gregorius. > > Hmmm. This needs qualifying... > > His tomb carries the inscription: > > GREGORIO XIII PONT.MAX. > > This expands to: > > GREGORIO XIII PONTIFEX MAXIMUS > > I have to admit to anglicizing names for > this list and would write 'Rome' rather > than 'Roma' despite the latter being the > correct Latin and Italian. > > Accordingly, your hero is Pope Gregory XIII > to me, at least when I remember to key in > the X :-) > > Very best wishes > Frank > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Republican Calendar, Year 231
Again my reply to Favio didn’t post. I don’t know why, but now I’m trying again to post it: , Favio— . You wrote: . [quote] The idea of reviving the Rep. Calendar (together with the corresponding Greg. Calendar) is that of an intellectual fun [/quote] . Undenniably so. . [quote] If you really wanted a calendar to be hooked with precision to the declination curves, I believe that the most authoritative is the Persian Calendar, still in use in Iran and Afghanistan, which uses the names of the zodiac for its months, that is, equating what gnomonists usually do. [/quote] . Yes, the Solar Haji calendar of Persia is accurate too. . I don’t know whether the Indian National Calendar or the Solar Haji is more accurate. . The Solar Haji uses a pure astronomical yearstart, & that makes it a fraction of a day more accurate. . Also, it includes a 29-day month. If the Indian National Calendar changes the 29 day month to 30 days, to keep all the months to 30 or 31 days (maybe for the convenience of monthly-payments), that would amount to some loss of accuracy. . But it seems to me that they said that the Solar Haji’s 29-day month is the last month of their year, which would be the ecliptic month of Pisces. But the shortest month of the year should be the one that includes our orbital perihelion….& isn’t that in Sagittarius or Capricorn. . Anyway, those two calendars are the most accurate day-count calendars. (as opposed to ecliptic-month systems that start the year at the exact moment of a solstice or equinox). . [quote] I don't think that the creators of the Rep. Calendar had the intention of reinterpreting the names of the zodiacal months (30° of longitude) with those of their calendar… [/quote . Maybe not explicitly, but of course they were intentionally measuring the same ecliptic-months that the traditional Aries-Pisces ecliptic-months measure. …but the FRC of course does so with a day-count calendar, so the months aren’t exactly the same. . [quote] If I really had to make some considerations on declination curves, I must say that lately I have rediscovered the use of these curves to define diurnal arcs of whole hours, i.e. selecting the declination values corresponding to diurnal arcs of whole hours and indicating this duration on the curves. [/quote] . But, we have the hour-lines to tell the hours. . Do you mean have a declination-line for each hour? But that would unacceptably clutter the dial, because there are so many hours in a half-year. …& look at how little hour-accuracy there’d be, with those very closely-spaced hourly declination-lines. That doesn’t sound feasible for sundial timekeeping. . [quote] There are not many sundials with these features but they exist and provide useful and not commonly available information (Sundial Atlas DE2758, CZ218, AT1291, IT14055, FR4881). [/quote] . I tried to find those dials at the Sundial-Atlas, but I couldn’t find a search-provision there. . [quote] On the Rep. Cal. 230, today is the day of 'celebration of convictions' :-) [/quote] . An appropriate day-name for this day when calendrical preferences are being discussed. . Wishing you a good year. . Wishing you good new ecliptic-month of Scorpio, the month before Sagittarius, the run-up to the Solstice upturn. . Wishing you a good Celtic New-Year, at Samhain . Ecliptic-Month Virgo, degree 28 . Michael On Tue, Sep 20, 2022 at 9:08 AM fabio.sav...@nonvedolora.it < fabio.sav...@nonvedolora.it> wrote: > Dear Michael > > The idea of reviving the Rep. Calendar (together with the corresponding > Greg. Calendar) is that of an intellectual fun and I would be amazed to > discover other implications. > > There are many calendars still in use in the world even if to give us an > appointment it has become common to refer to the Gregorian Calendar. > If you really wanted a calendar to be hooked with precision to the > declination curves, I believe that the most authoritative is the Persian > Calendar, still in use in Iran and Afghanistan, which uses the names of > the zodiac for its months, that is, equating what gnomonists usually do. > > I don't think that the creators of the Rep. Calendar had the intention > of reinterpreting the names of the zodiacal months (30° of longitude) > with those of their calendar even if, despite a bit of approximation, > these name could be a curious and entertaining option for people fasting > in astronomy but able to perceive the meaning of these names. > With all the limitations of this option by varying the latitude. > > If I really had to make some considerations on declination curves, I > must say that lately I have rediscovered the use of these curves to > define diurnal arcs of whole hours, i.e. selecting the declination > values corresponding to diurnal arcs of whole hours and indicating this > duration on the curves. > There are not many sundials with these features but they exist and > provide useful and not commonly
Re: Republican Calendar, Year 231
On Tue, Sep 20, 2022 at 4:44 AM Frank King wrote: > Dear Michael, > > I agree with much of what you say about the > French Republican Calendar but, importantly, > you say nothing about how this calendar > relates to sundials. Let me explain in > simple steps: > > 1. Sketch an outline vertical sundial with > seven declination curves and a single > hour line, at 12 noon. > > 2. The seven curves mark the boundaries of > six regions. Note each region is divided > into two parts by the 12 noon hour line. > > 3. We have 12 spaces. Now write the label > CAPRICORN in the top left space. This > is the first astronomical month after > the winter solstice. > > 4. In the five spaces underneath, you write > the names AQUARIUS to GEMINI. > > 5. On the right hand side you start at the > bottom and work up with the names CANCER > to SAGITTARIUS at the top. > > 6. This sundial will now tell you which > astronomical month you are in. Of > course you need to know whether the > solar declination is increasing or > decreasing but everyone who reads > this mailing list will know that :-) > > 7. Now, just for a moment, we do something > VERY SILLY. We replace the labels with > the names of the Gregorian months. So, > replace the label CAPRICORN with the > label JANUARY so on. > > 8. Notice that for about two-thirds of > JANUARY the sun really is in CAPRICORN > so this silly sundial actually gives > the correct Gregorian month about 67% > of the year. > > 9. NOW for the clever bit. Without changing > ANY detail of the specification of the > Gregorian Calendar (which you clearly > want to keep) you follow the precedent > set by your hero Pope Gregory III. Just > once, you cut 10 days from the year. We > could do this anywhere but let's cut > 10 days from March. JUST ONCE! > > 10. We now find the March Equinox is right > at the end of March so APRIL almost > exactly coincides with ARIES. > > 11. We find that each Gregorian month now > almost (but not quite) overlaps the > corresponding astronomical month. > > 12. This way, our 12 spaces really can be > labelled JANUARY to DECEMBER and the > sundial gives the correct Gregorian > month over 90% of the time. > > This makes life MUCH EASIER for sundial > designers who want their sundials to tell > the date, at least approximately. It is > almost impossible to estimate the date > to better than two or three days close > to the solstices so this calendar would > be quite usable. > > OK. Now for the bit you won't like... > > The adjusted Gregorian Calendar is very > nearly the same as the Republican Calendar. > The main differences are: > > 1. They made every month 30 days. > > 2. They changed the rules for leap years. > > The first change is not very important but > it is easier to teach children that EVERY > month is 30 days. > > The second change IS important because, by > insisting that every year begins on the > day of the September equinox, you don't > get wild swings in the dates of the starts > of the atarts of the astronomical months. > With the current Gregorian Calendar, the > September Equinox can be on any of the > dates 21, 22, 23 and 24 September and that > is just at the longitude of France. > > The Republican Calendar ensures that the > September Equinox is ALWAYS on the first > day of the first month of the year in > France. If you change longitude then > it will never drift more than a day > either side. > > Suggestion: > > Why don't you order one of these calendars > (English or Italian edition) then: > > LIVE WITH IT FOR A YEAR and, this > time next year, you can tell us all > how you got on with it :-) > > You might even enjoy the pictures and the > way the months work out. > > As others have said: this calendar is > GREAT FUN. > > Have a good year! > > Frank > > Frank King > Cambridge, U.K. > > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Republican Calendar, Year 231
I tried postings replies to both Frank & Favio in one post, & it didn’t work. Neither reply posted. So now I’m starting over, postings them sseparately. This reply is to Frank, & my reply to Favio will immediately subsequently be posted. I hope that these replies will post this time. Hi Frank— . Thanks for your reply. At first I thought that you were posting to point out my error, & it’s a relief that that isn’t so. Here’s what my error was: . I said that the ecliptic-month of Libra will start (in our Pacific Daylight-Savings time here) on September 23rd, some minutes after 3 a.m. I made that error because I was looking at October instead of September. . So, the time that I reported was the day of the month & the time of day at which the ecliptic month of Scorpio starts in October. . The correct time of the beginning of the ecliptic-month of Libra this year is September 22nd, at 6:04 p.m., in our Pacific Daylight Savings Time. . That’s September 23rd, at 1:04 a.m. in UTC. …or 01:04 in 24-hour time. . I’m replying inline so that I don’t miss any comments that I mean to reply to: . [quote] you say nothing about how this calendar relates to sundials. [/quote] . I mentioned that the FRC approximates the ecliptic-months, so I didn’t completely leave that out. . I agree with your description of a sundial’s declination-lines. . …7 of them if you just want to demarcate the 12 ecliptic-months. . …except that, often or usually, the old sundials labeled the ecliptic-months by their _symbols_ rather than their names. …as will my next sundial. . [quote] 7. Now, just for a moment, we do something VERY SILLY. We replace the labels with the names of the Gregorian months. So, replace the label CAPRICORN with the label JANUARY so on. [/quote] . I would never do that. . For one thing: . I prefer demarcating & labeling the ecliptic months, because: . 1. Calendars tell you the Roman month, & so why not let the sundial tell you the ecliptic-month. . 2. Telling the ecliptic-month is more accurate, because of course the relation between ecliptic-months & Roman months varies from year to year. . For another thing: . If someone would rather that the sundial give Roman months instead of ecliptic-months, then the sundial should give them the Roman months as accurately as possible !!! . The Roman months could be useful to someone who wanted to orient a portable window-sill dial or portable window-table dial by rotating it till it tells the right date. Though I myself prefer ecliptic-months for that purpose too, probably a lot of people would rather just use the Roman months. So, if you tell Roman months, then tell them as accurately as possible. . [quote] 8. Notice that for about two-thirds of JANUARY the sun really is in CAPRICORN so this silly sundial actually gives the correct Gregorian month about 67% of the year. [/quote] . Not good enough, especially if someone is using it to orient a portable table dial or windowsill dial. . [quote] 9. NOW for the clever bit. Without changing ANY detail of the specification of the Gregorian Calendar (which you clearly want to keep) you follow the precedent set by your hero Pope Gregory III… [/quote] . First, I doubt that he called himself Gregory, or that others did in those days. . His name was Gregorius. . Secondly, Pope Gregorius & his astronomers accomplished something important & distinctly-desirable, when they re-set the Julian calendar to its original relation to the Solar ecliptic-longitude . …& additionally improved the leapyear-rule to make it stay that way. . (no arithmetical rule will do that perfectly, but the Gregorian leapyear-does an excellent job. . Though, ideally, I prefer my own yearstart rule , which maximizes both accuracy & simplicity, the Gregorian leapyear-rule is undeniably good enough.) . I should add that I never call it the “Gregorian Calendar”. It’s the Julian Calendar, with the Gregorian re-alignment with the original Julian Calendar. I don’t call it “the Julian Calendar”, because “Julian Calendar” is always used for referring to the drifting & drifted Julian Calendar, used until the Gregorian reform. . I usually call it the Roman Calendar, or sometimes the Roman-Gregorian Calendar. I guess it could also be called the Julian Calendar with Gregorian restored seasonal-alignment. . I don’t agree that your proposed displacement of the Julian months is acceptably small. Even the proposed leapweek fixed-calendars only have 3.5 days max error. 10 days displacement would be significant, unprecedented & excessive. . After all, fixing a cumulative-drift of that magnitude was the reason why the Gregorian reform was deemed necessary. When Summer’s reliably consistent warm weather starts 10 days after the Summer-Solstice, we definitely notice that it didn’t start at the solstice. . [quote] 12. This way, our 12 spaces really can be
Re: Republican Calendar, Year 231
On Tue, Sep 20, 2022 at 9:08 AM fabio.sav...@nonvedolora.it < fabio.sav...@nonvedolora.it> wrote: > Dear Michael > > The idea of reviving the Rep. Calendar (together with the corresponding > Greg. Calendar) is that of an intellectual fun and I would be amazed to > discover other implications. > > There are many calendars still in use in the world even if to give us an > appointment it has become common to refer to the Gregorian Calendar. > If you really wanted a calendar to be hooked with precision to the > declination curves, I believe that the most authoritative is the Persian > Calendar, still in use in Iran and Afghanistan, which uses the names of > the zodiac for its months, that is, equating what gnomonists usually do. > > I don't think that the creators of the Rep. Calendar had the intention > of reinterpreting the names of the zodiacal months (30° of longitude) > with those of their calendar even if, despite a bit of approximation, > these name could be a curious and entertaining option for people fasting > in astronomy but able to perceive the meaning of these names. > With all the limitations of this option by varying the latitude. > > If I really had to make some considerations on declination curves, I > must say that lately I have rediscovered the use of these curves to > define diurnal arcs of whole hours, i.e. selecting the declination > values corresponding to diurnal arcs of whole hours and indicating this > duration on the curves. > There are not many sundials with these features but they exist and > provide useful and not commonly available information (Sundial Atlas > DE2758, CZ218, AT1291, IT14055, FR4881). > On the Rep. Cal. 230, today is the day of 'celebration of convictions' :-) > > ciao Fabio > > -- > Fabio Savian > fabio.sav...@nonvedolora.it > www.nonvedolora.eu > Paderno Dugnano, Milano, Italy > 45° 34' 9'' N, 9° 9' 54'' E, UTC +1 (DST +2) > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Fwd: Republican Calendar, Year 231
-- Forwarded message - From: Michael Ossipoff Date: Sun, Sep 18, 2022 at 2:50 PM Subject: Re: Republican Calendar, Year 231 To: Jack Aubert I should add that it seems to me that that earlier Roman Calendar only had 10 months. I prefer our Julian Calendar (with its Gregorian-restored alignment with the original Julian Calendar. I prefer it because of its February & April positioning. The earlier 10-month one didn’t even have February. On Sun, Sep 18, 2022 at 2:31 PM Michael Ossipoff wrote: > Pre-Julian…As you probably know, the Romans earlier had a calendar that > started at the Vernal Equinox. …with March 1st. > > That’s why September, October, November & December are so-named. > > …& so, resetting it wouldn’t be a problem. Just start the year as close as > possible to the Vernal Equinox. > > You could do that by the FRC’s method: March 1st would be the day that > contains the Vernal Equinox. …or better yet, the day that starts closest > to Vernal Equinox. > > …the actual astronomical Vernal Equinox. > > …or an arithmetical-approximation. Most calendars us an approximation. > e.g, The Gregorian rule was designed to approximate having the Vernal > Equinox on March 21st, because that’s when it was in the Julian Calendar. > > You could just say that, the calendar’s first year starts at that year’s > Vernal Equinox. > > & that each year starts on the day that starts closest to N days after the > previous one. > > …where N is the actual length (including the fraction) of a Vernal Equinox > tropical-year ( the duration between successive Vernal Equinoxes). > > That’s if you want to optimize for minimum calendrical-drift-rate of the > Vernal Equinox. > > If you want to minimize the average calendrical-drift over all the year’s > days, then use, for N, the length of the Mean Tropical Year. It’s about > 365.2422 days, but you could look it up for more accuracy. > > Likewise, the length of the Vernal Equinox tropical year can be looked up. > > BTW, the tropical year’s length, reckoned at different Solar ecliptic > longitudes, differs due to precession of the equinoxes & the ellipticity of > our orbit. > > The tropical year-lengths are all gradually changing, largely because of > precision of the apsides. > > Currently, the most nearly constant-length tropical year is the north > solstice tropical year. > > I.e. the summer solstice of the Nortern Hemispher > > > > > On Sun, Sep 18, 2022 at 5:49 AM Jack Aubert wrote: > >> Michael, >> >> >> >> I don’t think anybody is seriously contemplating calendar reform. I got >> a copy of the English version of the French Republican calendar from Frank >> King and It is hanging on a wall in my house. I love it because it is >> historically interesting and, in retrospect, amusingly goofy.The names >> of the months were parodied by contemporaneous English writers as >> adjectives like “sneezy, chilly, and breezy.” I would actually love to >> have a French version if anybody publishes one. It would have to retain >> the juxtaposition of the normal calendar with the FRC calendar so you can >> tell what today’s day and month would have been called. >> >> >> >> I wonder if anybody can figure out a way to juxtapose a pre-Julian Roman >> calendar onto a modern calendar. I think it would have to be arbitrarily >> reset somehow rather than fast forwarded. >> >> >> >> Jack Aubert >> >> >> >> *From:* sundial *On Behalf Of *Michael >> Ossipoff >> *Sent:* Saturday, September 17, 2022 9:02 PM >> *To:* fabio.sav...@nonvedolora.it >> *Cc:* Sundial sundiallist >> *Subject:* Re: Republican Calendar, Year 231 >> >> >> >> . >> >> The first thing I want to emphasize is that calendar-reform is not going >> to happen. What to do? Just deal with the calendar that we have…the one >> that we’ve had for two millennia.(…but with its Gregorian-modernized >> leapyear-system). Don’t waste your time on calendar-reform, because, for >> one thing, it isn’t going to happen. >> >> . >> >> But suppose that there’s an alternative calendar that you like. Calendar >> reform advocates are notoriously un-cooperative among eachother, & that >> further eliminates any chance of reform. But, even if the calendar were >> changed, then with the many different proposals around, what is the chance >> that the one that you’d like would be the one that somehow got adopted? >> Zilch. So that’s another reason to forget calendar-reform & just deal with >> the calendar that we have, the 2000-year-ol
Re: Republican Calendar, Year 231
Pre-Julian…As you probably know, the Romans earlier had a calendar that started at the Vernal Equinox. …with March 1st. That’s why September, October, November & December are so-named. …& so, resetting it wouldn’t be a problem. Just start the year as close as possible to the Vernal Equinox. You could do that by the FRC’s method: March 1st would be the day that contains the Vernal Equinox. …or better yet, the day that starts closest to Vernal Equinox. …the actual astronomical Vernal Equinox. …or an arithmetical-approximation. Most calendars us an approximation. e.g, The Gregorian rule was designed to approximate having the Vernal Equinox on March 21st, because that’s when it was in the Julian Calendar. You could just say that, the calendar’s first year starts at that year’s Vernal Equinox. & that each year starts on the day that starts closest to N days after the previous one. …where N is the actual length (including the fraction) of a Vernal Equinox tropical-year ( the duration between successive Vernal Equinoxes). That’s if you want to optimize for minimum calendrical-drift-rate of the Vernal Equinox. If you want to minimize the average calendrical-drift over all the year’s days, then use, for N, the length of the Mean Tropical Year. It’s about 365.2422 days, but you could look it up for more accuracy. Likewise, the length of the Vernal Equinox tropical year can be looked up. BTW, the tropical year’s length, reckoned at different Solar ecliptic longitudes, differs due to precession of the equinoxes & the ellipticity of our orbit. The tropical year-lengths are all gradually changing, largely because of precision of the apsides. Currently, the most nearly constant-length tropical year is the north solstice tropical year. I.e. the summer solstice of the Nortern Hemispher On Sun, Sep 18, 2022 at 5:49 AM Jack Aubert wrote: > Michael, > > > > I don’t think anybody is seriously contemplating calendar reform. I got a > copy of the English version of the French Republican calendar from Frank > King and It is hanging on a wall in my house. I love it because it is > historically interesting and, in retrospect, amusingly goofy.The names > of the months were parodied by contemporaneous English writers as > adjectives like “sneezy, chilly, and breezy.” I would actually love to > have a French version if anybody publishes one. It would have to retain > the juxtaposition of the normal calendar with the FRC calendar so you can > tell what today’s day and month would have been called. > > > > I wonder if anybody can figure out a way to juxtapose a pre-Julian Roman > calendar onto a modern calendar. I think it would have to be arbitrarily > reset somehow rather than fast forwarded. > > > > Jack Aubert > > > > *From:* sundial *On Behalf Of *Michael > Ossipoff > *Sent:* Saturday, September 17, 2022 9:02 PM > *To:* fabio.sav...@nonvedolora.it > *Cc:* Sundial sundiallist > *Subject:* Re: Republican Calendar, Year 231 > > > > . > > The first thing I want to emphasize is that calendar-reform is not going > to happen. What to do? Just deal with the calendar that we have…the one > that we’ve had for two millennia.(…but with its Gregorian-modernized > leapyear-system). Don’t waste your time on calendar-reform, because, for > one thing, it isn’t going to happen. > > . > > But suppose that there’s an alternative calendar that you like. Calendar > reform advocates are notoriously un-cooperative among eachother, & that > further eliminates any chance of reform. But, even if the calendar were > changed, then with the many different proposals around, what is the chance > that the one that you’d like would be the one that somehow got adopted? > Zilch. So that’s another reason to forget calendar-reform & just deal with > the calendar that we have, the 2000-year-old Roman Calendar. > > . > > The OP was advocating for the French Republican Calendar, translated into > your particular country’s language. > > . > > …but would its seasons be relevant to those who reside south of the > equator, or in the tropical regions? No. > > . > > It would be a seasonal calendar based on the seasons of one particular > lat-band. Hardly something that could be called internationally-fair or > meaningful. > > . > > But let’s look at some other attributes of the French Republican Calendar > (FRC): > > . > > It starts its year at the Autumnal Equinox, for those north of the > equator. (A more generally meaningful name for that equinox would be the > Southward-Equinox.) > > . > > Why? Well, the French Republican government started around that time of > the year. That was a commendable government, & an improvement on what it > replaced, but is it
Re: Republican Calendar, Year 231
Well, sundials often have solar-declination lines, & the old sundials (& the best modern ones too) often use those declination-lines to demarcate the ecliptic-months (the astrologers’ tropical-signs, from Aries to Pisces), labeled with the old symbols for them. . So that subject is certainly not off-topic here. . About solar-declination: . During the waxing-half of the year (…from Winter-Solstice to Summer-Solstice) increasing Solar declination is the most relevant calendrical numerical fact. I like to announce, at forums, when the Solar-declination passes certain landmarks. . For example, during the first waxing astronomical quarter there are days when the Solar declination has gone 1/3, 1/2, & 2/3 of the way from its Winter-Solstice value to its Spring-Equinox value. . Those three significant transitional days are all in February. . And, during the 2nd waxing astronomical quarter, there are days when the Solar declination has gone `1/3, 1/2, & 2/3 of the way from its Spring-Equinox value to its Summer-Solstice Value. . Very nearly, those three transitional days are all in April (the 2/3 point is actually usually in the very first days of May). . So, for Solar declination, in the 1st & 2nd waxing quarters respectively, February & April are the significant transitional-months for Solar declination. . Well, the Romans, too, felt that February was a significant seasonal transitional month, which is why they had the Februa celebration over that period.…because they regarded the Februa time to be so significant that they later designated a month to encompass it…February. . April is pretty much symmetrically across the equinox from February, due to the Roman months having roughly equal length. …& so, just as February is the transitional month in the 1st waxing quarter, so April is the transitional month in the 2nd waxing quarter. . Much has been written, by Spencer, Leigh Hunt & other early authors, about the unique characters of February & April. As we all know, the first signs of approaching Spring are in February, the first refreshingly-nice days. . April is the month when genuine Spring tentatively begins to start. . The ancient Celts celebrated their mid-quarter seasonal-holiday of Imbolc…a celebration of the beginning of that significant transitional period in the 1st waxing-quarter. . The Celts also celebrated another mid-quarter seasonal holiday, Beltane, in the early first days of our May. … i.e. immediately after April’s modest & tentative beginning of Spring. Beltane celebrates the time when full Spring is here. . Imbolc is very close to the day when the Solar declination is 1/3 of the way from its Winter-Solstice value to its Spring-Equinox value. Beltane is even closer to the day when the Solar declination is 2/3 of the way from its Spring-Equinox value to its Summer-Solstice value. . So, whether judged by Solar declination, or by seasonal nature & character, Imbolc & Beltane mark the ends of the transition, from the first signs of improvement from unmitigated winter, up to the arrival of full Spring. . The ancient Celts considered the mid-quarter holidays, which included Imbolc, Beltane & Samhain, to be their favorite seasonal-holidays. . (The other of the 4 Celtic mid-quarter holidays is Lughnasadh, at the beginning of our August, typically very close to the year’s peak temperature.) . It’s because of the delightful transitional-months, February & April, that I like our Roman Calendar, and don’t wish to change it. . But that’s just for the waxing quarters. . Right now we aren’t in the waxing-quarters. We’re in the first waning-quarter, near to that quarter’s end. . During this waning half of the year, it seems to me that the old ecliptic-months (the astrologers’ tropical signs) are more relevant & significant. . As I mentioned, this is relevant to sundials, because old sundials often use their declination-lines to demarcate the ecliptic-months. . Each ecliptic-month is a third of an astronomical quarter. For example, the current ecliptic month of Virgo is the last 3rd of the first waning astronomical-quarter. . On September 23rd, at 3:36 a.m. PDT, the ecliptic-month of Libra will begin. . Libra is the 1st third of the 2nd waning quarter. Thus, the ecliptic-months, dividing the astronomical-quarters into 3rds, are the months that neatly divide the seasonal year. I prefer them, in this waning half of the year, as indication of where we are in the seasonal year. . I hasten to emphasize that the ecliptic-months weren’t designed to be a civil-calendar. Civil-calendars are day-count calendars. The astronomical quarters & their divisions, the ecliptic-months, are based on the Sun’s ecliptic-longitude, rather being defined by a day-count. . But, though the ecliptic-months aren’t designed, intended or offered as a civil-calendar, they still, to me, make more sense as the way of saying where we are in this waning half of the year. .
Re: Republican Calendar, Year 231
. The first thing I want to emphasize is that calendar-reform is not going to happen. What to do? Just deal with the calendar that we have…the one that we’ve had for two millennia.(…but with its Gregorian-modernized leapyear-system). Don’t waste your time on calendar-reform, because, for one thing, it isn’t going to happen. . But suppose that there’s an alternative calendar that you like. Calendar reform advocates are notoriously un-cooperative among eachother, & that further eliminates any chance of reform. But, even if the calendar were changed, then with the many different proposals around, what is the chance that the one that you’d like would be the one that somehow got adopted? Zilch. So that’s another reason to forget calendar-reform & just deal with the calendar that we have, the 2000-year-old Roman Calendar. . The OP was advocating for the French Republican Calendar, translated into your particular country’s language. . …but would its seasons be relevant to those who reside south of the equator, or in the tropical regions? No. . It would be a seasonal calendar based on the seasons of one particular lat-band. Hardly something that could be called internationally-fair or meaningful. . But let’s look at some other attributes of the French Republican Calendar (FRC): . It starts its year at the Autumnal Equinox, for those north of the equator. (A more generally meaningful name for that equinox would be the Southward-Equinox.) . Why? Well, the French Republican government started around that time of the year. That was a commendable government, & an improvement on what it replaced, but is its commemoration really what we need as the basis of our year-start choice? . There are good arguments for starting the year at the northern-hemisphere’s Vernal-Equinox, Winter-Solstice, or Summer-Solstice...or at the ancient Celts’ year-start at their Samhain holiday, which corresponds to our Holloween...or at the start of October, the Roman month that contains Samhain...or at the start of Scorpio the ecliptic-month that contains Samhain. But I’ll spare you the year-start discussion, because, for one thing there isn’t going to be a new calendar. . Resuming the attributes of the FRC: . The FRC is a year of 12 months of exactly 30 days each. Seems like a nice aesthetic simplification. But it leaves 5 or 6 days that aren’t any day of the week, & don’t belong to any month …not so neat after-all. . Days that aren’t any day-of-the-week are called “blank-days”. They’re a mess, & that’s too obvious to need any explanation. . But, whatever reform-calendar you might like, its unlikely that it would be the one adopted, among the many proposals. …as if there were even any chance of any new calendar being adopted anyway. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Computing hour lines for horizontal sundials
As others have pointed out, you don’t need the logarithms. Tables of logarithms, trig-functions, & logs of trig-functions aren’t needed now that we have scientific-calculators, computers, spreadsheets, etc. Just use the trig-functions directly, as the others have said. . You made a good choice when you chose the Horizontal-Dial. There are good reasons why it’s the most popular stationary dial. . For one thing, it’s the easiest one to build, & also the easiest to set up. . For another thing, the marking of its hour-lines is easily explained . Additionally, it can be read from any direction (though you have to stand fairly near to it), & it tells time whenever the Sun is up (unless it’s shaded by something). . About the explanation of the marking of the Horizontal-Dial’s hour-lines: . Start with a Disk-Equatorial. It’s a circular disk with equally-spaced hour lines radially marked around the gnomon that passes through the disk’s center, perpendicularly to the disk. It’s mounted so that the disk is parallel to the equator. It has a stick-gnomon going through it, through its center, perpendicular to the disk, & therefore parallel to the Earth’s axis. . The relation between the gnomon-stick’s length down from the lower face of the disk, & the disk’s diameter can be chosen so that when the device is laid on the ground, resting on the disk-edge & on the bottom-end of the long gnomon-stick, the gnomon will be parallel to the Earth’s axis . Disk-Equatorials have been mounted directly on the ground in that form. I once read that dials of that type were the earliest known sundials. . So, to make a Horizontal-Dial from an Equatorial-Disk Dial of that type: . Extend, project, the hour-lines to the ground. . The projected lines will intersect the ground along an east-west line. . To each of those intersections, draw a line from the point where the bottom-end of the gnomon-stick touches the ground. . Those are the hour-lines of the Horizontal-Dial. . The 6:00 line wouldn’t intersect the ground, because the line would be horizontal, but it’s evident that, the closer the time is to 6:00, the more closely the direction of the Horizontal-Dial’s hour-line approaches perpendicular to the noon hour-line. So just make the 6:00 hour-line perpendicular to the hour-line. (That’s neatly automatically achieved by the formula.) . Of course, on the summer side of the equinoxes, the day will start before 6:00 a.m., & end after 6:00 p.m. For those times’ hour-lines, just (for example) extend the 7:00 a.m. hour-line across the dial-plate, to make the 7:00 p.m. line. …doing the same for the other p.m. times that have sunshine. . When you read the definitions of the sine & the tangent, it will be obvious that the formula is just a mathematical expression of the above-described method for constructing the hour-lines of the Horizontal Dial. On Tue, Aug 9, 2022 at 1:50 AM Bryan Mumford wrote: > I’m working from Albert Waugh’s book “Sun dials, Their Theory and > Construction”. On page 45 he presents a method for computing hour lines. I > lack significant math skills, but I know how to work Excel. I don’t > understand how he is calculating these values. > > He says, for example, that “log tan t” of 7°30’ is 9.11943. > > In my simple-minded way I asked Excel to show me log(tan(7)) and got a > very different value. > I tried converting 7°30’ to radians and that didn’t get any closer. > > How can I calculate "log tan t" or "log sin latitude” with Excel to get > the values he shows? > > I anticipate further problems with the last two columns, but you have to > start somewhere…. > > - Bryan > > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Right ascension on sundials
On Tue, Jun 7, 2022 at 11:15 AM Dan-George Uza wrote: > Hello, > > Are there sundials showing the Sun's right ascension? Can you please post > a photo? Thanks! > > Dan Uza > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > You could show R.A. Instead of declination or ecliptic longitude (Zodiac sign), but the latter are more often of seasonal interest. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: U.S. Senate approves bill to make daylight saving time permanent
Thanks for the good news that year-round DST is in process & might be enacted. . Here’s why I prefer year-round DST to year-round ST: . 1. Being out in the dark in early morning is safer than being out in the dark in the evening. . 2. Artificial lighting, and especially modern electric artificial-lighting, has moved us very far from the Sun’s time. Year-round DST would move us back closer to the Sun’s time. Yes, scientists, & especially astronomers, dislike advanced-time, because it sounds inelegant. But, for civil time, it seems to me that closeness to nature’s time is more important. . Sure, people could just change their schedules in the early direction, instead of changing the clocks. But how feasible would that be? Better to just advance the clocks. I don’t believe in standard-time sundials. They make no sense to me. Sundials are for Local True Solar Time. If you want clock-time, look at a clock. …or correct sundial-time for EqT & longitude-correction. . Of course French Hours are what’s popular for Sundials, & also what I prefer. . Temporary-Hours: In earlier centuries, in agricultural societies, it might have had much practical value to measure the progress of the day by what percentage of the day has passed. “The day (sunrise to sunset) is ¾ past, & I’ve done ¾ of the plowing that I intended.” . But now, measuring the day by what percentage of it has passed feels, to me, pessimistic, and an unproductive attitude. That isn’t something that I want to know. So I prefer French Hours. . But, for me, a really deluxe Sundial would, additionally tell, in the morning, how many equal-hours have passes since sunrise; &, in the afternoon, how many equal-hours remain till sunset. The latter could be of practical interest, & the former of interest too. Michael Ossipoff On Tue, Mar 15, 2022 at 5:51 PM Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > > It seems the USA may be getting ready to abolish seasonal clock > changes. The proposal has just passed in the Senate but still has to be > accepted by the House of Representatives, so we can't celebrate yet. ( > > https://www.reuters.com/world/us/us-senate-approves-bill-that-would-make-daylight-savings-time-permanent-2023-2022-03-15/ > ) > > If it happens, Canada would quickly follow. In fact, here in British > Columbia it's already in law that we will switch to permanent DST once > Washington (state), Oregon and California have switched. The EU is > already on the same path but things have got bogged down with some > member countries yet to decide which timezone to adopt. EU-wide > preparations were further delayed due to the pandemic ( > > https://www.thelocal.it/20211029/clocks-to-go-back-in-italy-despite-eu-deal-on-scrapping-hour-change/ > ). > > I would have preferred permanent Standard Time over permanent > Daylight-saving Time but, even so, I hope the plans proceed. It will > certainly simplify the my designs for Civil Time sundials and Equation > Of Time signage. > > Cheers, Steve > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Is this an educational sundial, or a 'NON-dial'?
> > Any non-declining dial...i.e. any dial whose style is in the > meridional-plane, can be easily & briefly explained as a Horizontal Dial at > a different latitude. Sorry, I meant to say "...any dial for which the normal to the dial's flat shadow-receiving plane is in the meridional-plane..." On Sun, Apr 4, 2021 at 6:53 PM Michael Ossipoff wrote: > I agree about Analemmataic Dials not being educational, except for > students who are interested in the trig and willing to listen to, study and > work on the subject. Some are, and for them it would be great. > > But for most people, it's just a magic-trick, as you pointed out. The > Analemmatic has the advantage of being vandalism-proof, but it seems to me > that there's no satisfaction, fun or interest for someone in a dial unless > they want to hear the explanation for why it works...and few would be > willing to listen to the construction-explanation of the Analemmatic. > > The Horizontal-Dial has a brief, clear and simple explanation, deriving > from lines drawn on the horizontal surface to where a Polar Dial intersects > that surface. ...and the Polar Dial of course derive from an Equalorial's > hour marks projected from the disk or cylinder onto a polar-parallel plane. > > Any non-declining dial...i.e. any dial whose style is in the > meridional-plane, can be easily & briefly explained as a Horizontal Dial at > a different latitude. > > On Sat, Apr 3, 2021 at 11:34 PM Peter Mayer > wrote: > >> Hi Rudolph, >> >> I DO like 'Undial'! Thanks for reminding us of your inspired name. >> >> best wishes, >> >> Peter >> On 4/04/2021 5:16:57, R. Hooijenga wrote: >> >> For this kind of instrument, I personally like to use the term 'Undial'. >> >> So far, it didn't catch on, however - pity! >> >> >> >> Good Easter, >> >> Rudolf Hooijenga 52 30 N 4 40 E >> >> >> >> -Oorspronkelijk bericht- >> >> Van: sundial Namens Linda Reid >> >> Verzonden: zaterdag 3 april 2021 20:04 >> >> Aan: sundial@uni-koeln.de >> >> Onderwerp: Is this an educational sundial, or a 'NON-dial'? >> >> >> >> >> >> [...] but looking at the illustration on the front cover, it seems to be >> a 'NON-dial'! >> >> ---https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> -- >> --- >> Peter Mayer >> Department of Politics & International Relations (POLIR) >> School of Social Scienceshttp://www.arts.adelaide.edu.au/polis/ >> The University of Adelaide, AUSTRALIA 5005 >> Ph : +61 8 8313 5609 >> Fax : +61 8 8313 3443 >> e-mail: peter.ma...@adelaide.edu.au >> CRICOS Provider Number 00123M >> --- >> >> This email message is intended only for the addressee(s) >> and contains information that may be confidential >> and/or copyright. If you are not the intended recipient >> please notify the sender by reply email >> and immediately delete this email. >> Use, disclosure or reproduction of this email by anyone >> other than the intended recipient(s) is strictly prohibited. >> No representation is made that this email or any attachment >> are free of viruses. Virus scanning is recommended and is the >> responsibility of the recipient. >> --https://www.adelaide.edu.au/study/ >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Is this an educational sundial, or a 'NON-dial'?
On Sun, Apr 4, 2021 at 6:57 PM Michael Ossipoff wrote: > ...and the Horizontal-Dial, if not in shade, tells time whenever the Sun > is up, and is readable from every direction, if the person is sufficiently > close to it....and, in general, the Flat-Dials are the easiest-built > dials. > ...and , with suitable orientation, can excel in distance-readability > > On Sat, Apr 3, 2021 at 11:34 PM Peter Mayer > wrote: > >> Hi Rudolph, >> >> I DO like 'Undial'! Thanks for reminding us of your inspired name. >> >> best wishes, >> >> Peter >> On 4/04/2021 5:16:57, R. Hooijenga wrote: >> >> For this kind of instrument, I personally like to use the term 'Undial'. >> >> So far, it didn't catch on, however - pity! >> >> >> >> Good Easter, >> >> Rudolf Hooijenga 52 30 N 4 40 E >> >> >> >> -Oorspronkelijk bericht- >> >> Van: sundial Namens Linda Reid >> >> Verzonden: zaterdag 3 april 2021 20:04 >> >> Aan: sundial@uni-koeln.de >> >> Onderwerp: Is this an educational sundial, or a 'NON-dial'? >> >> >> >> >> >> [...] but looking at the illustration on the front cover, it seems to be >> a 'NON-dial'! >> >> ---https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> -- >> --- >> Peter Mayer >> Department of Politics & International Relations (POLIR) >> School of Social Scienceshttp://www.arts.adelaide.edu.au/polis/ >> The University of Adelaide, AUSTRALIA 5005 >> Ph : +61 8 8313 5609 >> Fax : +61 8 8313 3443 >> e-mail: peter.ma...@adelaide.edu.au >> CRICOS Provider Number 00123M >> --- >> >> This email message is intended only for the addressee(s) >> and contains information that may be confidential >> and/or copyright. If you are not the intended recipient >> please notify the sender by reply email >> and immediately delete this email. >> Use, disclosure or reproduction of this email by anyone >> other than the intended recipient(s) is strictly prohibited. >> No representation is made that this email or any attachment >> are free of viruses. Virus scanning is recommended and is the >> responsibility of the recipient. >> --https://www.adelaide.edu.au/study/ >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Is this an educational sundial, or a 'NON-dial'?
...and the Horizontal-Dial, if not in shade, tells time whenever the Sun is up, and is readable from every direction, if the person is sufficiently close to it....and, in general, the Flat-Dials are the easiest-built dials. On Sat, Apr 3, 2021 at 11:34 PM Peter Mayer wrote: > Hi Rudolph, > > I DO like 'Undial'! Thanks for reminding us of your inspired name. > > best wishes, > > Peter > On 4/04/2021 5:16:57, R. Hooijenga wrote: > > For this kind of instrument, I personally like to use the term 'Undial'. > > So far, it didn't catch on, however - pity! > > > > Good Easter, > > Rudolf Hooijenga 52 30 N 4 40 E > > > > -Oorspronkelijk bericht- > > Van: sundial Namens Linda Reid > > Verzonden: zaterdag 3 april 2021 20:04 > > Aan: sundial@uni-koeln.de > > Onderwerp: Is this an educational sundial, or a 'NON-dial'? > > > > > > [...] but looking at the illustration on the front cover, it seems to be > a 'NON-dial'! > > ---https://lists.uni-koeln.de/mailman/listinfo/sundial > > -- > --- > Peter Mayer > Department of Politics & International Relations (POLIR) > School of Social Scienceshttp://www.arts.adelaide.edu.au/polis/ > The University of Adelaide, AUSTRALIA 5005 > Ph : +61 8 8313 5609 > Fax : +61 8 8313 3443 > e-mail: peter.ma...@adelaide.edu.au > CRICOS Provider Number 00123M > --- > > This email message is intended only for the addressee(s) > and contains information that may be confidential > and/or copyright. If you are not the intended recipient > please notify the sender by reply email > and immediately delete this email. > Use, disclosure or reproduction of this email by anyone > other than the intended recipient(s) is strictly prohibited. > No representation is made that this email or any attachment > are free of viruses. Virus scanning is recommended and is the > responsibility of the recipient. > --https://www.adelaide.edu.au/study/ > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Is this an educational sundial, or a 'NON-dial'?
I agree about Analemmataic Dials not being educational, except for students who are interested in the trig and willing to listen to, study and work on the subject. Some are, and for them it would be great. But for most people, it's just a magic-trick, as you pointed out. The Analemmatic has the advantage of being vandalism-proof, but it seems to me that there's no satisfaction, fun or interest for someone in a dial unless they want to hear the explanation for why it works...and few would be willing to listen to the construction-explanation of the Analemmatic. The Horizontal-Dial has a brief, clear and simple explanation, deriving from lines drawn on the horizontal surface to where a Polar Dial intersects that surface. ...and the Polar Dial of course derive from an Equalorial's hour marks projected from the disk or cylinder onto a polar-parallel plane. Any non-declining dial...i.e. any dial whose style is in the meridional-plane, can be easily & briefly explained as a Horizontal Dial at a different latitude. On Sat, Apr 3, 2021 at 11:34 PM Peter Mayer wrote: > Hi Rudolph, > > I DO like 'Undial'! Thanks for reminding us of your inspired name. > > best wishes, > > Peter > On 4/04/2021 5:16:57, R. Hooijenga wrote: > > For this kind of instrument, I personally like to use the term 'Undial'. > > So far, it didn't catch on, however - pity! > > > > Good Easter, > > Rudolf Hooijenga 52 30 N 4 40 E > > > > -Oorspronkelijk bericht- > > Van: sundial Namens Linda Reid > > Verzonden: zaterdag 3 april 2021 20:04 > > Aan: sundial@uni-koeln.de > > Onderwerp: Is this an educational sundial, or a 'NON-dial'? > > > > > > [...] but looking at the illustration on the front cover, it seems to be > a 'NON-dial'! > > ---https://lists.uni-koeln.de/mailman/listinfo/sundial > > -- > --- > Peter Mayer > Department of Politics & International Relations (POLIR) > School of Social Scienceshttp://www.arts.adelaide.edu.au/polis/ > The University of Adelaide, AUSTRALIA 5005 > Ph : +61 8 8313 5609 > Fax : +61 8 8313 3443 > e-mail: peter.ma...@adelaide.edu.au > CRICOS Provider Number 00123M > --- > > This email message is intended only for the addressee(s) > and contains information that may be confidential > and/or copyright. If you are not the intended recipient > please notify the sender by reply email > and immediately delete this email. > Use, disclosure or reproduction of this email by anyone > other than the intended recipient(s) is strictly prohibited. > No representation is made that this email or any attachment > are free of viruses. Virus scanning is recommended and is the > responsibility of the recipient. > --https://www.adelaide.edu.au/study/ > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Can This New Map Fix Our Distorted Views of the World?
Sorry, but the mapping of the Earth in two circular pieces goes back at least to the 1500s or 1400s. . The difference is that the 1400s & 1500s maps showed two side-by-side circles, making it much easier to use, rather than having it on opposite sides of a disk. . The favorite ancient way to map half of the Earth was the Stereographic Projection. Suppose you place a plane surface in contact with the globe. >From a point on the side directly opposite the contact-point, project, onto the plane, the half of the globe that's closest to the plane. That's the Stereographic projection. . Its date-of-origin isn't known, but it's amcient. One reason for its popularity was its good shapes, and, at any particular point, the same scale in every direcition. Later, in the 18th century, Halley proved that the Stereographic has that property (called "conformality"). . As mentioned above the usual way of displaying the Stereographic was to show two side-by-side circles. And it was, and is, mlre practical to use equatorial-aspect: The two circular maps, each of half of the Earth, are each centered on a point on the equator. . So, sorry, the "new" map isn't new. It's just more inconvenient, having half of the Earth on the other side of the paper. . The article didn't say anything about the map they mentioned, other than that it was a polar map. They didn't say whether it's equal-area, conformal, or neither. (Regrettably, the current fashion for world maps is "compromise" maps that are neither.) . Yes, it's common for people to complain that the Mercator distorts areas. I've got big news for you: Every flat map distorts something. With a conformal map (such as Mercator), at any given point, the scale is the same in every direction, resulting in good small-region shapes, directions, and relative-distances. The opposite would be equal-area maps, on which all areas are in the correct proportion. Obviously, conformal maps and equal-area maps are both useful for different purposes. If you use world maps, you should have both. . With Mercator (or any conformal map) the only distortion consists of differential magnification.. Of course, Mercator's Canada is shaped wrong, due to the huge magnification of its arctic region. But, othet than Canada, the shapes are pretty-much excellent on Mercator. . Anyway, yes sometimes the shadow-receiving surface of a sundial consists of a world-map, chosen so that a nodus-shadow will tell what point on the Earth the Sun is direcly over. The map would have to be on the right projection. Sure, a polar map of suitable projection would serve that purpose on a disk-equatorial map, but the article said nothing about the projection of the map that it mentioned. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: request
Determining how much time error, at a certain time, a given azimuth-alignment-error will cause, or what azimuth-alignment error would cause a certain time error at a certain time--That isn't an unusual kind of problem. But, if you want to use clock-time to set a sundial, then just rotate the dial till it says the correct Local-True-Solar-Time. Of course you find the correct Local-True-Solar-Time from the clock-time, by means of EqT and longitude. In earlier times, that would often be done by using a noon-line to determine Local-True-Solar-Noon. The noon-line drawn north-south to the base of a vertical, which could be a window-edge or a vertical edge of a square-cross-section pole. Determining north without a clock or watch can be done by marking the position of the shadow of some point like the tip of a twig, or a corner at the top of a square post. Mark the position of the tip-shadow in the morning, measure from it to the point directly under the shadow-casting point (which could be determined by a plulmbline). In the afternoon, when the distance from tip-shadow to the sub-tip point is the same as before, mark the position of the tip-shadow again. The line between the marks is east-west, and a line perpendicular to it is north-south. That's a way to determine north-south for making a noon-line, by which to align a sundial at Local-True-Solar-Noon. Alternatively, one could just wait till it's getting close to noon, and then start marking the tip-position, and note when it's at its shortest, at which time it's to the north of the sub-tip point. Michael Ossipoff On Sat, Aug 8, 2020 at 12:59 PM André Reekmqns wrote: > Looking for the 3 pages article published in BSS or NASS 10 years? about > rectifying a misaligned pole-style horizontal or vertical sundial. > > > > André Reekmans > > Sundial Society of Flanders, Belgium. > > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Time problem
According to a graph from Lascar, in 1986, the greater obliquity of the elcliptic 700 years ago would, even at the Winter-Solstice, only change Sunrise-time (in local true Solar time) at lat 46 by about half a minute. In fact, even with the greatest obliquity that ever occurs in the current cycle, that lat 46 Winter-Solstice Sunrise time would only differ from now by about 6 minutes. So evidently one of your sources has simply made a big error of some kind. On Tue, Jun 30, 2020 at 10:06 AM Ross Sinclair Caldwell < belmu...@hotmail.com> wrote: > Hi Jack, > > Thanks for thinking about this problem. > > It isn't the clock time, in any system, that matters here. The biographer > - Pier Candido Decembrio - reports only that it was six minutes after > sunrise. So all that matters is to determine when sunrise was, by any > system we can, in order to be able to put the data into an astronomy > program or a helpful spreadsheet using medieval values, like Lars Gislén's > "Astromodels" for the Alfonsine Tables, which those astrologers probably > used. http://home.thep.lu.se/~larsg/Site/download.html > > The problem I encounter is that two very apparently reliable sources give > different times for the sunrise from Milan on that day, once the date is > corrected to Gregorian and given a Julian day. > > The NOAA site gives 06:22 CET, the program Stellarium gives 06:00. On > Stellarium, today I went back year by year, and noticed that they not only > automatically switch to Julian calendar before 15 October 1582, but also > make a change in times in the year 1847. In both Béziers, where I live, > and Milan, sunrise for 1 October is 07:22 (what is the historical basis for > this additional hour?) in 1848, but goes to 06:00 in 1847 and all the years > thence back to 1583 (within a minute or so, for the quarter days leading to > a leap year). In 1582, 1 October sunrise in Milan is 06:12, so you have to > know to change to the Julian calendar date of 23 September to get the right > sunrise, which is 06:01. > > Hank showed from the "old" NOAA Earth System Research Lab page > https://www.esrl.noaa.gov/gmd/grad/solcalc/sunrise.html that putting in > the data with the UTC offset at +0.61 for Milan (-0.61 for American users) > at that longitude produced the "correct" time at 05:58, so with a few more > decimals it would be within a minute of the Stellarium and YourSky programs > (which rigorously uses Meeus, I believe). > > I am leaning to a 06:00 as the consensus. > > Ross > > > -- > *De :* Jack Aubert > *Envoyé :* mardi 30 juin 2020 15:31 > *À :* 'Ross Sinclair Caldwell' ; 'Michael Ossipoff' > > *Cc :* 'sundial list sundials' > *Objet :* RE: Time problem > > > I have been thinking about this problem but I may not be understanding it > correctly. I think you want to find out what time sunrise was on September > 23 in 1392. Because of the change from Julian to Gregorian dates, this > corresponds to our October 1. On October 1, a real clock in Milan this > year would not tell quite the same time as a municipal clock in 1392, > though. > > > > We can easily correct for daylight saving time. The second thing to > consider would be the equation of time. But it has changed very little > between 1329 and now, so sunrise on October 1 1329 in Milan should be > almost the same time as it is now, so if you could transport a modern clock > to Milan in 1329, it would show sunrise at very close to the same time as > it does now. But this would not necessarily be the case in 1392. At that > time, clocks would normally not take the equation of time into account at > all. Since they were not very accurate over an extended period, they would > have had to be adjusted frequently using a sundial. So the municipal clock > would probably have shown noon at what we would call 12:11. It is possible > that a clock used by an astronomer might make the adjustment using a > contemporaneous equation of time table (which would have been less accurate > than our calculation) but this seems unlikely. > > > > The other thing to take into account is Milan's longitude. At 9.11 > degrees East, Milan is six degrees from the 15 degree time zone center, for > a clock offset of 24 minutes. So a calculation for modern civil time at > that location should include both the longitude and equation of time. A > calculation of contemporary civil time would obviously not have included a > time zone offset, I think, should not have included the equation of time > either. > > > > It sounds to me as if the programs may be handling the longitude offset, > and possibly the equation of time differently. > > > > Does this make sense
Re: Time problem
Okay, but there's the inaccuracy of the clocks in those days, and the importance of that would depend on how they determined Sunrise. I guess they set the clocks by sundial or noon-mark, but, as you said, it depends on how often they set them. Anyway, the difference between the NOAA Sunrise-time, and the one calculated by the planetarium-programs could result from the planetarium-programs not taking into account the changes in orbit or obliquity. I'd expect that the NOAA figure would be more reliable. Sunrise & Sunset times are usually calculated using a standard value for atmospheric refraction at the horizon. The usual assumption is that the refraction is 34 minutes and that the Sun's apparent semi-diameter is 16 minutes. Maybe NOAA used a calculated semi-diameter instead of the standard 16 minutes. You don't have sufficiently reliably accurate information for a horoscope accurate to the minute, and another reason for that is that unusual atmospheric refractivity could change Sunrise-time by minutes. Michael On Mon, Jun 29, 2020 at 1:09 PM Ross Sinclair Caldwell wrote: > > Hi Michael, > > Also, when they said that he was born a certain number of minutes after > Sunrise, how did they determine that? By judging when it seemed to be > Sunrise, when the Sun appeared over the trees, mountains or buildings, or > by calculating Sunrise-time based on a 14th century estimate of Milan's > longiitude? And were they minutes of equal-hours time, or of > temporary-hours time? > > I can answer some of those questions with reasonable certainty. > > For minutes, they used an equal-hour 24 hour clock, beginning a half-hour > after sunset the previous day. That is, the clock would strike "1" at, say, > at our 20:45 on that particular day (30 September Gregorian). Of course it > was constantly adjusted, with what frequency I don't know. Obviously it > depended on the season, but there must have also been a regular schedule of > maintenance for the mechanism. I don't know if an example of such a > schedule survives from any of these early clocks, since Europe generally > moved to the equal-hour 24-hour day starting at midnight in the sixteenth > century. > > For sunrise, it is a flat view east of Milan, and the part of the castle > where he is reported to have been born was one of the highest places in the > city. From the top of one of the four corner towers, you would see clear to > the eastern horizon. But it is possible they made a calculation rather than > an observation, and so perhaps it was theoretical rather than observed, > even if they used an hourglass with minutes we would recognize. Even if it > were a cloudy morning, they knew what time the sun rose. > > For what value it had, the propaganda, since he was the second son, he was > not expected to inherit the throne, so there was less reason to fudge the > data to make him appear better than he was. The day of birth was a public > announcement; the time was apparently a closely guarded secret, since > astrology could be a political weapon. > > Ross > -- > *De :* Michael Ossipoff > *Envoyé :* lundi 29 juin 2020 18:39 > *À :* Ross Sinclair Caldwell > *Cc :* sundial list sundials > *Objet :* Re: Time problem > > Of course, even if the Earth's orbit didn't change, no civil calendar > keeps a constant relation between date and ecliptic-longitude. So you'd > have to determine the calendar's date-ecliptic-longitude displacement for > the date of interest. > . > But the Earth's orbit does change. Our orbit's eccentricity, and the > relation between the apsides and the equinoxes have been steadily changing > since the 14th century. ...as has the obliquity of the ecliptic. > . > Might some of the commercially-available planetarium-programs disregard > that? Sure. At least some of those programs ignore changes in the > precessional-rate, so why expect them to take into account the changing > eccentricity, apsides/equinoxes relation, and obliquity of the ecliptic? > . > Also, when they said that he was born a certain number of minutes after > Sunrise, how did they determine that? By judging when it seemed to be > Sunrise, when the Sun appeared over the trees, mountains or buildings, or > by calculating Sunrise-time based on a 14th century estimate of Milan's > longiitude? And were they minutes of equal-hours time, or of > temporary-hours time? > . > Michael Ossipoff > > > > > > On Mon, Jun 29, 2020 at 5:23 AM Ross Sinclair Caldwell < > belmu...@hotmail.com> wrote: > > Hi diallists, > > This is not a sundial problem, but a time discrepancy I don't understand > between NOAA sunrise calculations and the results of two reliable > planetarium programs, Stellarium and YourSky (part
Re: Time problem
Of course, even if the Earth's orbit didn't change, no civil calendar keeps
a constant relation between date and ecliptic-longitude. So you'd have to
determine the calendar's date-ecliptic-longitude displacement for the date
of interest.
.
But the Earth's orbit does change. Our orbit's eccentricity, and the
relation between the apsides and the equinoxes have been steadily changing
since the 14th century. ...as has the obliquity of the ecliptic.
.
Might some of the commercially-available planetarium-programs disregard
that? Sure. At least some of those programs ignore changes in the
precessional-rate, so why expect them to take into account the changing
eccentricity, apsides/equinoxes relation, and obliquity of the ecliptic?
.
Also, when they said that he was born a certain number of minutes after
Sunrise, how did they determine that? By judging when it seemed to be
Sunrise, when the Sun appeared over the trees, mountains or buildings, or
by calculating Sunrise-time based on a 14th century estimate of Milan's
longiitude? And were they minutes of equal-hours time, or of
temporary-hours time?
.
Michael Ossipoff
On Mon, Jun 29, 2020 at 5:23 AM Ross Sinclair Caldwell
wrote:
> Hi diallists,
>
> This is not a sundial problem, but a time discrepancy I don't understand
> between NOAA sunrise calculations and the results of two reliable
> planetarium programs, Stellarium and YourSky (part of HomePlanet).
> http://stellarium.org/ https://www.fourmilab.ch/yoursky/
> https://www.fourmilab.ch/homeplanet/
>
> In short, I am researching the biography of Filippo Maria Visconti
> (1392-1447), duke of Milan, and you probably know that these Italian
> princes relied heavily on astrology. So, Visconti's time of birth is known
> precisely - "six minutes after sunrise," Monday, 23 September, 1392. His
> natal chart was of course produced and interpreted, but it has been lost. I
> am trying to recreate it as it might have been done by a court astrologer
> of the time.
>
> First step - get the Gregorian equivalent, and the Julian day. This is 1
> October 1392 Gregorian, which is Julian day 2229751.5 (".5" because Julian
> days start on noon, and the .5 represents midnight, the beginning of 23
> September Julian/1 October Gregorian).
>
> Now, both Stellarium and YourSky automatically correct for the change from
> Julian calendar to Gregorian. That is, if you look at the sky for 15
> October 1582, and then go back one day, the calendar reads 4 October 1582.
> This was the change mandated by Pope Gregory, that Thursday 4 October 1582
> would be followed Friday 15 October 1582.
>
> So, there is no need to use 1 October 1392 for my purposes - both programs
> read 23 September as Julian day 2229751.5(etc).
>
> These programs give the sunrise in Milan on that date at 06:00 and 05:59
> respectively. Obviously they use an ideal horizon, but the view east from
> Milan is flat, so there is nothing delaying the appearance of the sun.
>
> Now,, when you go to NOAA's Solar Calculator, they use straight Gregorian
> dates. That is, you can get sunrise times for 5, 6, 7, etc. up to 14
> October, 1582. So you have to use the Gregorian equivalent of 23 September
> 1392, which is 1 October. https://www.esrl.noaa.gov/gmd/grad/solcalc/
>
> They give the sunrise time as 06:22 on 1 October 1392. If you are in doubt
> about the Gregorian/Julian switch, they give the time on 23 September as
> 06:12. Neither is in agreement, in any case, with the astronomy programs.
>
> Now, the difference between 1392 and today should be negligible in any
> case. We can just as well use this year's 1 October for the time of
> sunrise. Of course, it is 06:22 (or 07:22 since in 2020 Italy uses daylight
> saving time).
>
> In order to get a sunrise time of 06:22 on Stellarium, I have to push the
> date to 11 October.
>
> The problem is that both NOAA and the astronomy programs are right for me
> for sunrise and sunset in Béziers today (within a minute).
>
> So, the astronomy programs are apparently wrong for the 1392 date. This is
> not really ancient, so I wonder if anyone could suggest to me why it might
> be that there is 22 minutes' difference between these programs and the NOAA
> data for the same date?
>
> Thank you for any thoughts that anyone might have.
>
> Ross Caldwell
> 43.349399 3.22422981
> Béziers
> ---
> https://lists.uni-koeln.de/mailman/listinfo/sundial
>
>
---
https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Advice sought re:transparent sundial design
Steve-- Yes, undeniably the co-Italian hours have more practical use than Babylonian hours, as do the Temporary Hours that used to be standard before clocks came into use. For outdoor work like agriculture, or anything for which candle-light wasn't sufficient, of course it mattered very much how many hours were left before sunset(co-Italian), or what *percentage* of the day remained (Temporary-Hours). If you've plowed 1/3 of the field that needs plowing today, then it's desirable that not more than 1/3 of the day has elapsed. But I wouldn't choose Temporary Hours, because now the matter of how much of the day is gone seems like a negative thing to remind oneself of, and not the right way to regard the day or the time. Maybe that's why you don't like Babylonian Hours. What I like about Babylonian Hours is that it tells how young the day is, early in the morning. That's why I'd include it. Of course, with both Babylonian and co-Italian Hours, one could determine Temporary hours by: T = B/(B+CI) ...where T = Temporary B = Babylonian CI = co-Italian Michael Ossipoff Aprilis 23rd, 2020 Taurus 5th 18 Th On Wed, Apr 22, 2020 at 3:00 PM Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > Michael, > > For sure. > > I simply ignored the possibility of Babylonian Hours because I > personally don't think they have much practical use (to the extent that > any sundial has practical use these days). For a dial showing hours to > sunset, on the other hand, I do see some hint of practical use. It will > tell me if I have time to mow the lawn or finish painting the fence > before it gets dark, and so on. As well, for observers of some > religions, a sunset dial could be used to know approximately how much > time is left until, for example, the Sabbath starts or until a daytime > fast can be broken. > > Steve > > > > > > On 2020-04-22 5:52 a.m., Michael Ossipoff wrote: > > Because the dial is a translucent-double one, with gnomons on both > > sides of the dial-plate, it would tell time all day, and so it could > > give Babylonian-hours in addition to co-Italian hours. > > > > On a single dial, with everything on the same dial-face, it would > > avoid clutter to show Babylonian hours only in the morning, and > > co-Italian hours only in the evening. But, with the very wide hole in > > the wall, there's easily room for 3 dials, with one exclusively for > > Babylonian and co-Italian, and so it wouldn't be cluttered to show > > both for all day. > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Denizli sundial
Karlheinz-- I don't claim to be a Greek-scholar, but, now that you mention it, that could be a theta at the beginning of the word along the Summer-Solstice line. . But I just don't find the iota and sigma at the beginning of the word along the equinox line. . But none of that even matters if, as you said, it isn't even a 2000-year-old dial, and is only from the Roman era. What a disappointment. But thanks for pointing it out anyway. . Michael Ossipoff Aprilis 10th, 2020 Aries 22nd 16 F . On Fri, Apr 10, 2020 at 2:27 AM Karlheinz Schaldach < karlheinz_schald...@t-online.de> wrote: > I would like to add two arguments to the questions under discussion*:* > > 1. Prof. Şimşek said: “On the North Parados passage in the Western > Theater, which dates back to the Hellenistic Era, in the ancient city we > have found a spherical sundial facing south, which we believe to be 2,020 > years old. > > This is a kind of conclusion which does not help by dating the dial. A > comparison with similar specimens reveals that it was probably done around > 200 – 400 CE. > > 2. “Inscribed on the dial are the Greek word ‘Ksimerini’, or winter on > the upper part; ‘Isimerini’, or solstice, which denotes the equality of day > and night in the middle; and ‘Terini’, or summer in the bottom.” > > I read (ΤΡΟΠH) ΧΕ(Ι)ΜΕΡΙΝH / IΣΗΜΕΡΙΝH / (ΤΡΟΠH) ΘΕΡΙΝH. > > These are the names of the solstices and the equinoxes. What is > conspicuous is the missing of I in χειμερινή (it should be written with > diacritic signs). That is another strong argument that it was done in the > Roman era. > > With best wishes > > Karlheinz Schaldach > > *From:* Michael Ossipoff > *Sent:* Friday, April 10, 2020 5:11 AM > *To:* Maes, F.W. > *Cc:* Sundial List > *Subject:* Re: Denizli sundial > > >> "Inscribed on the dial are the Greek word ‘Ksimerini’, or winter on the >> upper part >> > > No doubt "Merini" referring to "day", related to "Mera", meaning "Day", > combined with "Xi-", which must mean something like "longest". > > ; ‘Isimerini’, or solstice, which denotes the equality of day and night in >> the middle; and ‘Terini’, or summer in the bottom." >> > > The middle line is for the equinoxes, not a solstice. > > If it says "Isimerini", then that combines "-merini", referreing to "Day", > and something obviously likely to be related to "Iso-" which we all know to > mean "same" or "equal". > > >> Ksimerini would in Greek start with Ξ (ksi), but a close look at the >> initial, hi-res photo strongly suggests that the first character is X (chi) >> > > Yes, that column of horizontal lines is the Greek capital "Ksee" (as > pronounced in English). The lower case would look like a more or less > vertical squiggly line. It's pronounced like our English "X". > > Yes, the Greek letter written as "X", is pronounced like aspirated "k", as > in "Loch" or "Achtung". ...and its name "chi", is pronounced in English > with that consonant-sound, though we often hear it said as just a "k". > > I didn't notice the "T" in the word on the Summer-Solstice line. > > It looked. to me, just like Merine on the top 2 lines, and Erini on the > bottom--line. > > Michael Ossipoff > Aprilis 10th, 2020 > Aries 22nd > 16 F > > You wrote: > > , in accordance with what John Davis and John Wilson's wife read. > > So it seems the names are spelled as follows: > XIMEPINH = winter solstice > IΣHMEPINH = equinox > TEPINH = summer solstice > in which X is Greek chi, P is Greek rho, H is Greek eta. > > -- > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Denizli sundial
> > "Inscribed on the dial are the Greek word ‘Ksimerini’, or winter on the > upper part > No doubt "Merini" referring to "day", related to "Mera", meaning "Day", combined with "Xi-", which must mean something like "longest". ; ‘Isimerini’, or solstice, which denotes the equality of day and night in > the middle; and ‘Terini’, or summer in the bottom." > The middle line is for the equinoxes, not a solstice. If it says "Isimerini", then that combines "-merini", referreing to "Day", and something obviously likely to be related to "Iso-" which we all know to mean "same" or "equal". > Ksimerini would in Greek start with Ξ (ksi), but a close look at the > initial, hi-res photo strongly suggests that the first character is X (chi) > Yes, that column of horizontal lines is the Greek capital "Ksee" (as pronounced in English). The lower case would look like a more or less vertical squiggly line. It's pronounced like our English "X". Yes, the Greek letter written as "X", is pronounced like aspirated "k", as in "Loch" or "Achtung". ...and its name "chi", is pronounced in English with that consonant-sound, though we often hear it said as just a "k". I didn't notice the "T" in the word on the Summer-Solstice line. It looked. to me, just like Merine on the top 2 lines, and Erini on the bottom--line. Michael Ossipoff Aprilis 10th, 2020 Aries 22nd 16 F You wrote: , in accordance with what John Davis and John Wilson's wife read. So it seems the names are spelled as follows: XIMEPINH = winter solstice IΣHMEPINH = equinox TEPINH = summer solstice in which X is Greek chi, P is Greek rho, H is Greek eta. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re:
Along each declination-line, "Merine" is written (if, as it seems to me, H is an E). I used to know someone whose 1st language was Greek, and "Mera" means "Day". If the M is absent from the summer solstice line, maybe it got obliterated over the millennia. The declination-lines of course mark special days, and maybe that's all that "Merina" is saying. ...and surely it isn't really necessary to explicitly number the hour-lines. Maybe the user just counts them. Of course the dial is a Hemicycleum, the classical and ancient stationary-dial. It's said to have been introduced by Berosus in Chaldea, in the same century in which the article's dial was made. It seems to me that they said that the Hemicycleum and Hemisphereum were soon imported to and adopted by Greece, and later Rome. I read that the dial surface of both was spherical. Surely that would be a particularly difficult surface to carve accurately, but that's what they say. The Hemicycleum is my favorite stationary dial, and it's the next one that I'll make (but it will be cardboard & paper, or sheet-plastic, and the dial-surface will be cylindrical. Michael Ossipoff Aprilis 9th Aries 21st 16 Th On Thu, Apr 9, 2020 at 8:01 AM guerbabi ali via sundial < sundial@uni-koeln.de> wrote: > Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die > eigentliche Nachricht steht dadurch in einem Anhang. > > This message was wrapped to be DMARC compliant. The actual message > text is therefore in an attachment. > > > -- Forwarded message -- > From: guerbabi ali > To: John Davis , "sundial@uni-koeln.de" < > sundial@uni-koeln.de> > Cc: > Bcc: > Date: Thu, 9 Apr 2020 12:01:23 + (UTC) > Subject: Denizli sundial > > Dear John and members of the Sundial List, > > > > These are the greek names for the respective solstices and the equinoxes > carved on over 25 ancient sundials (planar and hollow), most of them are in > Sharon Gibbs’ book (from Delos: 1001, 1072, 4001; from Pompeii: 4007; from > Rome: 4008, 4009, 4010; from Ephesos: 3058: etc). > > As for the front face, normally it should be oblique in the plane of the > celestial equator, but it happens that some ancient conical and spherical > sundials are not. Here the image is misleading because the disappearance > of the corners can give the impression that the face is vertical. We > should have a side photo to know what it really is. > > > > Regards > > > > Ali Guerbabi > > 35.547 N / 6.16 E > > > Le jeudi 9 avril 2020 à 08:54:55 UTC+1, John Davis via sundial < > sundial@uni-koeln.de> a écrit : > > > Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die > eigentliche Nachricht steht dadurch in einem Anhang. > > This message was wrapped to be DMARC compliant. The actual message > text is therefore in an attachment. > Dear Frans, > > The picture that Dan-George pointed us to is excellent and intriguing too. > My reading of the lettering is slightly different from yours. Starting from > the top (presumably the winter solstice), I get > > X I M E P I N H >H M E P I N H >E P IN H > > where the columns represent the spaces between the hour lines. There could > be some misreadings here. It is clearly not the standard Greek system of > using the first letters of their alphabet as numbers but I don’t recognise > the names of the seasons either. Looking through Sharon Gibbs’ book, I > couldn’t find a similar set of inscriptions. Can any classical scholars > help us? > > As a second point, the front face of the marble looks to be vertical in > the photo but I found another view online which seems to show it cut back > at an oblique angle. Both forms of dial are known - which is this? > > Regards, > > John > — > Dr J Davis > Flowton Dials http://www.flowton-dials.co.uk/ > BSS Editor http://sundialsoc.org.uk/publications/the-bss-bulletin/ > > > On 8 Apr 2020, at 18:37, Maes, F.W. wrote: > > Dan-George, thank you for the link! That is a beautiful ancient scaphe > dial. > The article says: "The sundial features ... Greek names of seasons". I can > read a number of characters, which at all three date lines (equinox and > solstices) seem to include MEPINH. What season names are these? > > Keep healthy! > Frans Maes > > On Tue, Apr 7, 2020 at 12:33 PM Roser Raluy wrote: > > Thank you, it looks great! > Roser Raluy > > Missatge de Dan-George Uza del dia dt., 7 > d’abr. 2020 a les 10:12: > > Hello, I've just read about the discovery of an antique sundial in Turkey. > > > https://www.dailysabah.com/life/history/2000-year-old-sundial-unearthed-in-
Re: Aperture nodus geometry
Dan-- . If the hole is very small compared to the projection-distance, then the image of the Sun projected on the wall would be sharp and clear-edged, nearly free of fuzziness. Its size will be about 1/100 of the projection-distance. . The un-fuzziness of a small-aperture projection is the reason why they're used to get precise Solar noon from a noon-mark. . Englarging the aperture enlarges the image by the same amount, and of course makes it fuzzier, because each little element of the previous image is now duplicated over a region the size of the aperture. . In your example, the aperture is about twice the size of the tiny-aperture image. . Michael Ossipoff Aprilis 8th, 2020 Aries 20th 16 W . On Wed, Apr 8, 2020 at 12:05 PM Dan-George Uza wrote: > Hello, > > I'm a big fan of meridian lines inside churches and I know these are sort > of camera obscura sundials. > > While I understand the geometry behind pinhole camera projections I can't > seem to find any help on how the solar image forms after the rays pass a > sizeable aperture nodus (for example a vertical 25cm nodus projected onto a > wall 10 meters away) and how the ratio of hole size vs. projection distance > affects the size and fuzzyness of the final projected image. So what's the > geometry behind that? > > > PS: Some sources refer to the projected image as "stenopaic image". Is > this universally acceptable? > > -- > Dan-George Uza > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: A question abou scaphes
On Tue, Apr 7, 2020 at 12:24 PM Michael Ossipoff wrote: > ...and of course the surrounding flat-dials could, instead, be > Reclining-Declining Dials facing in the cardinal-directions. > > But the sphere-segment indentation surface gives a better continuous > system of dial-lines. > > On Tue, Apr 7, 2020 at 12:18 PM Michael Ossipoff > wrote: > >> If the indentation were a shallow rectangular hollow instead of a segment >> of a sphere, it would of course amount to several adjoined flat dials--a >> horizontal-dial surrounded by vertical-dials. >> >> Michael Ossipoff >> 16 Tu >> Aries 19th >> Aprilis 7th >> >> On Tue, Apr 7, 2020 at 7:07 AM Peter Mayer >> wrote: >> >>> Hi, >>> Dan-George Uza's recent post reminded me of a question I have. I was >>> looking at Mark Lennox-Boyd's lovely *Sundials* the other day, >>> especially photos of some of the beautiful Renaissance ivory diptychs, and >>> realised that I didn't understand the principles behind the small scaphes >>> on many dials. (Here's a Wikicommons photo of a Leonhard Miller dial). >>> The Greek and Roman scaphes, like the one in Dan-George's photo, were >>> hollow sections of either spheres or cones, with a gnomon at their centre. >>> Their mode of operation seems quite straight-forward. >>> But the scaphes in diptyches weren't like that. They appear to be tiny >>> slices of much larger spheres. And the gnomons are, of course, far from the >>> centre. The 'furniture' on several of them seems similar to stereographic >>> projections. But, since instrument-makers then were well able to make >>> astrolabes with stereographs, perhaps not. >>> So: can someone point me to an article which discusses these small >>> scaphes? Or, in the meantime, help me understand how and why they were >>> used? Why don't we make them any more? Or: are there any contemporary >>> examples, using, say, bowls, or bird-baths or skateboard parks? >>> best wishes, >>> >>> Peter >>> >>> --- >>> Peter Mayer >>> Department of Politics & International Relations (POLIR) >>> School of Social Scienceshttp://www.arts.adelaide.edu.au/polis/ >>> The University of Adelaide, AUSTRALIA 5005 >>> Ph : +61 8 8313 5609 >>> Fax : +61 8 8313 3443 >>> e-mail: peter.ma...@adelaide.edu.au >>> CRICOS Provider Number 00123M >>> --- >>> >>> This email message is intended only for the addressee(s) >>> and contains information that may be confidential >>> and/or copyright. If you are not the intended recipient >>> please notify the sender by reply email >>> and immediately delete this email. >>> Use, disclosure or reproduction of this email by anyone >>> other than the intended recipient(s) is strictly prohibited. >>> No representation is made that this email or any attachment >>> are free of viruses. Virus scanning is recommended and is the >>> responsibility of the recipient. >>> -- >>> >>> --- >>> https://lists.uni-koeln.de/mailman/listinfo/sundial >>> >>> --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: A question abou scaphes
If the indentation were a shallow rectangular hollow instead of a segment of a sphere, it would of course amount to several adjoined flat dials--a horizontal-dial surrounded by vertical-dials. Michael Ossipoff 16 Tu Aries 19th Aprilis 7th On Tue, Apr 7, 2020 at 7:07 AM Peter Mayer wrote: > Hi, > Dan-George Uza's recent post reminded me of a question I have. I was > looking at Mark Lennox-Boyd's lovely *Sundials* the other day, especially > photos of some of the beautiful Renaissance ivory diptychs, and realised > that I didn't understand the principles behind the small scaphes on many > dials. (Here's a Wikicommons photo of a Leonhard Miller dial). > The Greek and Roman scaphes, like the one in Dan-George's photo, were > hollow sections of either spheres or cones, with a gnomon at their centre. > Their mode of operation seems quite straight-forward. > But the scaphes in diptyches weren't like that. They appear to be tiny > slices of much larger spheres. And the gnomons are, of course, far from the > centre. The 'furniture' on several of them seems similar to stereographic > projections. But, since instrument-makers then were well able to make > astrolabes with stereographs, perhaps not. > So: can someone point me to an article which discusses these small > scaphes? Or, in the meantime, help me understand how and why they were > used? Why don't we make them any more? Or: are there any contemporary > examples, using, say, bowls, or bird-baths or skateboard parks? > best wishes, > > Peter > > --- > Peter Mayer > Department of Politics & International Relations (POLIR) > School of Social Scienceshttp://www.arts.adelaide.edu.au/polis/ > The University of Adelaide, AUSTRALIA 5005 > Ph : +61 8 8313 5609 > Fax : +61 8 8313 3443 > e-mail: peter.ma...@adelaide.edu.au > CRICOS Provider Number 00123M > --- > > This email message is intended only for the addressee(s) > and contains information that may be confidential > and/or copyright. If you are not the intended recipient > please notify the sender by reply email > and immediately delete this email. > Use, disclosure or reproduction of this email by anyone > other than the intended recipient(s) is strictly prohibited. > No representation is made that this email or any attachment > are free of viruses. Virus scanning is recommended and is the > responsibility of the recipient. > -- > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: A question abou scaphes
It seems to me that the indented dial-surface could serve a useful purpose, by ensuring that the nodus's shadow falls on that dial-surface whenever the Dyptich's flat horizontal surface has sunlight. . Maybe it's desired to make the indented dial-surface much larger than the hemispherical indentation that could be accomodated by the thickness of the horizontal plate of the Dyptich. . Of course not having the nodus at the center of the sphere would complicate the marking of the lines on the indented spherical surface, explaining why that isn't encountered more often. . It's related to stereographic lines, by having a projection-point not at the center of the sphere. It sounds like a great idea for a birdbath or bowl, but it might be too distracting for a skateboard-park. . Michael Ossipoff Aprilis 7th, 2020 16 Tu Aries 19th On Tue, Apr 7, 2020 at 7:07 AM Peter Mayer wrote: > Hi, > Dan-George Uza's recent post reminded me of a question I have. I was > looking at Mark Lennox-Boyd's lovely *Sundials* the other day, especially > photos of some of the beautiful Renaissance ivory diptychs, and realised > that I didn't understand the principles behind the small scaphes on many > dials. (Here's a Wikicommons photo of a Leonhard Miller dial). > The Greek and Roman scaphes, like the one in Dan-George's photo, were > hollow sections of either spheres or cones, with a gnomon at their centre. > Their mode of operation seems quite straight-forward. > But the scaphes in diptyches weren't like that. They appear to be tiny > slices of much larger spheres. And the gnomons are, of course, far from the > centre. The 'furniture' on several of them seems similar to stereographic > projections. But, since instrument-makers then were well able to make > astrolabes with stereographs, perhaps not. > So: can someone point me to an article which discusses these small > scaphes? Or, in the meantime, help me understand how and why they were > used? Why don't we make them any more? Or: are there any contemporary > examples, using, say, bowls, or bird-baths or skateboard parks? > best wishes, > > Peter > > --- > Peter Mayer > Department of Politics & International Relations (POLIR) > School of Social Scienceshttp://www.arts.adelaide.edu.au/polis/ > The University of Adelaide, AUSTRALIA 5005 > Ph : +61 8 8313 5609 > Fax : +61 8 8313 3443 > e-mail: peter.ma...@adelaide.edu.au > CRICOS Provider Number 00123M > --- > > This email message is intended only for the addressee(s) > and contains information that may be confidential > and/or copyright. If you are not the intended recipient > please notify the sender by reply email > and immediately delete this email. > Use, disclosure or reproduction of this email by anyone > other than the intended recipient(s) is strictly prohibited. > No representation is made that this email or any attachment > are free of viruses. Virus scanning is recommended and is the > responsibility of the recipient. > -- > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Sunrise time glitch?
Now the Solar declination is more than halfway from its Yul (Winter-Solstice) value to its Ostara (Spring-Equinox) value. And, in mid-latitudes (mid-lat U.S., and similar latitudes in Europe), the daily insolation (ground-warming sunlight received by the ground) has likewise passed the halfway point between its Yul and Ostara values. And, tomorrow, the daily insolation at that latitude will be half of its annual maximum. That is, it will have a value that's half of its value at Litha (Summer-Solstice). Tonight, Leo is the early-evening-rising ecliptic-constellation. Its early-evening-rising now, just before the beginning of the Roman month of Martius, heralds the evening-rising of Virgo just before the beginning of the Roman month of Aprilis. Of course, during Aprilis, Virgo will be rising in the early evening sky On Tue, Feb 25, 2020 at 2:00 PM Dan-George Uza wrote: > Hello all, > > While doing some research for a paper, a friend of mine noticed peculiar > differences regarding sunrise times for his city (Alba Iulia, Romania). > They occur both on TimeAndDate.com as well as suncalc.org and -so far I > can tell- only in Romanian cities (Berlin and Vienna are okay). > > I figure sunrise times should be pretty much the same except for the leap > year cycle, but for example between December 1st 1930 and December 1st 1931 > the times differ by more than 15 minutes. What could be the cause? > > I also looked at Gian Casalegno's Sun Ephemeris and all the times check > out neatly there. > > -- > Dan-George Uza > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Sunrise time glitch?
Dan-- Evidently those two sources you named got their result from the same other source, which had made an error....or else one of those two sources got their result from the other. If the two years are separated by a leapyear (but 1930 and 1931 aren't), then there could be a 3-day difference in the correspondence between date and ecliptic-longitude. But, since there was no leapyear between those two dates, there was just the 1/4 day displacement that occurs at the end of a common-year. That wouldn't be nearly enough to cause that difference in sunrise or sunset times. ...or a sufficient difference in the EqT. So, evidently someone's error got copied and thereby propagated. 10 Tu Pisces 7th Februarius 25th On Tue, Feb 25, 2020 at 2:00 PM Dan-George Uza wrote: > Hello all, > > While doing some research for a paper, a friend of mine noticed peculiar > differences regarding sunrise times for his city (Alba Iulia, Romania). > They occur both on TimeAndDate.com as well as suncalc.org and -so far I > can tell- only in Romanian cities (Berlin and Vienna are okay). > > I figure sunrise times should be pretty much the same except for the leap > year cycle, but for example between December 1st 1930 and December 1st 1931 > the times differ by more than 15 minutes. What could be the cause? > > I also looked at Gian Casalegno's Sun Ephemeris and all the times check > out neatly there. > > -- > Dan-George Uza > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Solar-Declination 1/3 of the way back up from Winter-Solstice
Yesterday the Solar-declination reached and passed the point 1/3 of the way, back up from the Winter-Solstice, toward the Celestial-Equator. 7 Th (South-Solstice WeekDate Calendar) Aquarius 19th (South-Solstice Ecliptic-Months Calendar) Februarius 7th (Roman-Gregorian Calendar) Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Some Portable Folded-Paper Flat-Dials
I'd just like to say a few more things about the portable folded-paper flat-dials. What interests me about them is that I like the Regiomontanus, as my favorite portable dial, and the most easily-built sundial of any category. But it's of interest how easily-built can be a portable-dial that doesn't lose accuracy near noon. ...because that could matter for modern urban applications, where public-transportation departures, appointments and events might be near noon. . I spoke of a 1-fold dial with a Horizontal-Dial on one surface and a vertical Polar-Dial on the other surface. I said that it wouldn't work in the manner that I'd described. I'd expected it to work with the top-edge of the vertical section as the gnomon, when use tipped-up as a Polar-Dial with both surfaces as polar-dial surfaces. . But it would work fine using a nodus at the middle of the connecting-thread (the thread that secures the right-angle fold). In that manner, it could work as a Horizontal-Dial and a vertical Polar-Dial, or, tipped-up, it could work as half of a Box Polar Dial. . A 2:1 paper rectangle is folded at the middle of its long-dimension, to make two mutually-perpendicular square surfaces. A thread connects the middle of their outer edges, and that thread has a nodus at its middle. . I call it the "corner-configuration" or "half-box configuration" . With one square horizontal, that square would have a Horizontal-Dial, and the other would have a vertical Polar-Dial. . Or the dial could be tipped up to make both surfaces polar-dials. . --- . To summarize the 3 folded-paper dial-configurations that I've described: . These 3 configurations each forms half of a right-square-prism, cut in half by a plane through its axis (analogous to the half of a right-circular-cylinder comprising a Cylindrical-Eauatorial Dial. . With the 1-fold configurations, the user's thumb, resisted by the connecting-thread, can hold the 2 surfaces apart at a right-angle. ...which worked fine for all of my corrugated-cardboard Tablet-Dials. . Orientation about the vertical axis is by means of the declination-lines, labeled by declination or (preferably) by the approximate date for each 1/12 of the year's ecliptic-longitude variation. . 1. Corner-Configuration or Half-Box configuration: . As described immediately above. . With one plane horizontal, it mignt not be necessary to have a plumb-line for leveling. With both planes polar, a plumb-line could orient the dial about the NS & EW axes. . 2. Box-Configuration: . A 2:1 rectangle is perpendicularly folded-up a quarter of its length from each end. . A thread connects the middles of the top-edges of the up-folded ends. The nodus is at the middle of that thread. . Disadvantage: . The 3 folds complicate things for a folded-paper dial. ...in the matter of holding the up-folded ends perpendicular to the base. That adds a whole qualitatively different design problem to a folded-paper dial. . Advangage: . Potentially convenient use, by its resemblence to Cylindrical-Equatorial and especially to a Box-Polar (...which is what it is when tipped up as a Polar-Dial). . Orientation with respect to EW & NS axes is as for the corner-configuration. . 3. V Configuration: . A 2:1 or 1:1 paper square is folded at-middle into a right-angle V. ...hand-held, with the fold-crease in the plane of the meridian, with the two dial-planes tipped equally from the plane of the meridian. . As with the Corner-Configuration, the right-angle is held by a thread connecting the middles of the outer-edges of the two sections. The user's thumb holds the two planes apart, resisted by the connecting-thread. . - . Each of these 3 configurations can be used in either of 2 orientations: . Horizontal: . One plane, or at least some of the edges, is/are horizontal. . Polar: . All of the planes are polar, parallel to the Earth's axis. . . Those combinations of configuration and orientation make 6 possible portable folded-paper flat-dials. . I'm not claiming that others aren't possible. . . The 1-fold configurations would be much easier to build, given the problem of keeping the box-configuration's two up-folded ends perpendicular to the plane between them. . In the horizontal-orientation, the corner-configuration looks easier to use than the V-configuration, because the corner-configuration has a horizontal surface, giving it easier leveling even without a plumb-line. (My Tablet-Dials were all 5-minutes-accurate without a plumb-line or spirit-level.) . Especially for the polar-orientation, the V-configuration has appeal. ...though, even there, the corner-configuration might be easier to orient about the polar-axis, due to the ramp-like orientation of one of its planes. . --- . Of course, for the dials in polar-orientation the line-construction is much easier to explain. In fact, it practially doesn't need any explanation. .
Some Portable Folded-Paper Flat-Dials
e suggested, which can be read more easily all year. . . For a stationary-dial, by some building-methods (such as joining slabs)the Box-Polar Dial might be easier to build than the Cylindrical-Equatorial Dial. . By some building-methods (such as molded Concrete)the Box-Polar doesn't look any easier to build than the Cylindrical-Equatorial. So, then, there'd be no reason to not build the Cylindrical-Equatorial. . 49 M November 25th 2328 UTC . Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Some Portable Folded-Paper Flat-Dials
I should add that the Folded-Paper Horizontal & Vertical-Polar Dial can also be made with just one fold: . A 2:1 paper rectanble is folded at its middle in a right-angle. . The fold is held by a thread connecting the middles of the top-edges of the two squares. . A nodus (bead or tied-short-thread) is at the middle of the connecting-thread. . For morning or afternoon, the dial is held with one square vertical and the other horizontal. For both morning and afternon, of course the horizongal square needs a horizontal dial drawing on it, and the vertical square needs a vertical-polar dial drawn on it. . So, it would be necessary to have separate pairs of dials drawn on the two sides of the rectangle, one for morning and one for evening. . That would necessitate adjusting the connecting-thread. The connecting-thread could be in the form of a loop, so that the fold could be reversed, using that same thread-loop. That thread-loop could have a nodus on each of its two opposite sides, so that the noduc could be correctly-positioned in morning or afternoon. . Of course, with both sides of the paper needed for the dials, a separate piece of paper would be needed for the tabulated EqT, and the tabulated decination or ecliptic-longitude. . 48 Su November 24th 2230 UTC . Michael Ossipof --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Some portable folded-paper flat-dials.
ifficult, but the orientation about the crease would be more difficult, and would probably require a plumb-line hanging from the middle (nodus) point of the connecting-thread. Such a plumb-line could achieve correct orientation about both axes (the crease and an EW axis). . - . Of course, alternatively, either of these dials could use the intersection of the connecting thread with the top-edge of the sunward square as the nodus. . - . On either of these dials, the declination-lines could be labled for declination, or for ecliptic-longitude (maybe by zodiac-sign, maybe by degree, maybe by numbered ecliptic-months in numbered quarters). Of course then ecliptic-longitude, instead of declination, would be listed in a table on the back of one of the squares. . An advantage of eclicptic-longitude is that it can be fairly-accurately estimated from the date. (...not that that would be necessary if ecliptic-longitude by date is tabulated on the back of one of the squares.) . 48 Su November 24th 2142 UTC . Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re:
I wrote: Hi Franco-- > Sorry to mis-write your name--I meant Francesco. 48 W November 20th 1649 UTC Michael Ossipoff On Wed, Nov 20, 2019 at 11:29 AM Michael Ossipoff wrote: > My dials will show 9 declination-lines: > > 1; Equinoxes, solstices, and half-solstice declinations > > 2. Declinations at the ecliptic-longitudes that divide each > astronomical-quarter (interval between an equinox and a solstice) into > thirds. > > So the dials will indicate solar-declination and solar-ecliptic-longitude > (expressed in thirds of an astronomical-quarter--the tropical signs of the > Zodiac, labeled with their traditional astrological symbols for the signs > of the Zodiac). > > The dials will also show Babylonian hours in the morning, and co-Italian > hours in the afternoon. > > The Cylindrical-Equatorial shows h and dec in a clear rectangular format, > and doesn't need explanation. > > The Horizontal Dial or course is the most easily-built stationary dial, > and is particularly-easily read from any direction by someone who is near > to it, and tells time whenever the Sun is above the horizon (except if it's > shaded at some times of day). > > A Cylindrical-Equatorial Dial can be built to tell time whenever the Sun > is above the horizon. The upper edge of the cylinder is trimmed horizontal, > and the nodus is a bead at the middle of a string transversely across the > cylinder, with the nodus-bead positioned on the cylinder's axis normal to > the dial's equator-line. The nodus-bead is also level with the > horizontally-trimmed top-edge of the cylinder. > > This Cylindricald-Equatorial is similar to the ancient Hemicycleum. > ...differing from it by using a cylindrical surface instead of a spherical > surface; using a string-mounted nodus-bead instead of a stick-gnomon (which > I consider to be an eye-injury-hazard); and not being cut-away as the > Hemicyclea usually were. > > 48 M > November 20th > 1628 UTC > Michael Ossipoff > > > > On Wed, Nov 20, 2019 at 11:00 AM Michael Ossipoff > wrote: > >> Hi Franco-- >> . >> I like explanations that can be understood by anyone from at least >> pre-secondary-school. I believe that such people can understand the sundial >> and map-projection explanations that I'd use. >> . >> To whom would I give explanations?: Primarily to my girlfriend. She >> isn't interested in math, but that doeesn't mean that those explanations >> wouldn't be understandable to her if she's interested in them, interested >> in lisening to them. >> . >> I mentioned to her that our windowsill sundial would be a >> Cylindrical-Equatorial Dial, because it doesn't need any explanation, >> because it shows the Sun's position in the most direct way. She replied >> that she has nothing against explanation of the Horizontal-Dial, its >> hour-lines and declination-lines, and considers it interesting. >> . >> So the first windowsill dial here will be a Cylindrical-Equatorial Dial, >> followed by a Horizontal Dial. >> . >> In general, I believe that these subjects can be explained to anyone who >> is interested in hearing the explanation. >> . >> So I'd offer these explanations to anyone to whom I'd suggest or offer a >> sundial or map-projection. I like the idea of a sundial or displayed map >> being accompanied by a pamphlet or a page that tells its >> construction-formula derivation-explanation. >> . >> Some say that people aren't interested in explanations, but I suggest >> that, rather, they're often just resigned to things being not explainable >> to them. I believe that, when shown a sundial or map, they'd like it >> explained. >> . >> It seems to me that every park, library, museum, plaza, and other >> public-spaces, should have a sundial. >> . >> >> -- >> >> I'm not familiar with those softare products, but I'd have no objecion to >> their use. I'd use drawings, but of course that software could be helpful >> too, showing things in ways other than what a drawing can show. >> >> 48 W >> November 20th >> 1600 UTC >> . >> Michael Ossipoff >> > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re:
My dials will show 9 declination-lines: 1; Equinoxes, solstices, and half-solstice declinations 2. Declinations at the ecliptic-longitudes that divide each astronomical-quarter (interval between an equinox and a solstice) into thirds. So the dials will indicate solar-declination and solar-ecliptic-longitude (expressed in thirds of an astronomical-quarter--the tropical signs of the Zodiac, labeled with their traditional astrological symbols for the signs of the Zodiac). The dials will also show Babylonian hours in the morning, and co-Italian hours in the afternoon. The Cylindrical-Equatorial shows h and dec in a clear rectangular format, and doesn't need explanation. The Horizontal Dial or course is the most easily-built stationary dial, and is particularly-easily read from any direction by someone who is near to it, and tells time whenever the Sun is above the horizon (except if it's shaded at some times of day). A Cylindrical-Equatorial Dial can be built to tell time whenever the Sun is above the horizon. The upper edge of the cylinder is trimmed horizontal, and the nodus is a bead at the middle of a string transversely across the cylinder, with the nodus-bead positioned on the cylinder's axis normal to the dial's equator-line. The nodus-bead is also level with the horizontally-trimmed top-edge of the cylinder. This Cylindricald-Equatorial is similar to the ancient Hemicycleum. ...differing from it by using a cylindrical surface instead of a spherical surface; using a string-mounted nodus-bead instead of a stick-gnomon (which I consider to be an eye-injury-hazard); and not being cut-away as the Hemicyclea usually were. 48 M November 20th 1628 UTC Michael Ossipoff On Wed, Nov 20, 2019 at 11:00 AM Michael Ossipoff wrote: > Hi Franco-- > . > I like explanations that can be understood by anyone from at least > pre-secondary-school. I believe that such people can understand the sundial > and map-projection explanations that I'd use. > . > To whom would I give explanations?: Primarily to my girlfriend. She isn't > interested in math, but that doeesn't mean that those explanations wouldn't > be understandable to her if she's interested in them, interested in > lisening to them. > . > I mentioned to her that our windowsill sundial would be a > Cylindrical-Equatorial Dial, because it doesn't need any explanation, > because it shows the Sun's position in the most direct way. She replied > that she has nothing against explanation of the Horizontal-Dial, its > hour-lines and declination-lines, and considers it interesting. > . > So the first windowsill dial here will be a Cylindrical-Equatorial Dial, > followed by a Horizontal Dial. > . > In general, I believe that these subjects can be explained to anyone who > is interested in hearing the explanation. > . > So I'd offer these explanations to anyone to whom I'd suggest or offer a > sundial or map-projection. I like the idea of a sundial or displayed map > being accompanied by a pamphlet or a page that tells its > construction-formula derivation-explanation. > . > Some say that people aren't interested in explanations, but I suggest > that, rather, they're often just resigned to things being not explainable > to them. I believe that, when shown a sundial or map, they'd like it > explained. > . > It seems to me that every park, library, museum, plaza, and other > public-spaces, should have a sundial. > . > > -- > > I'm not familiar with those softare products, but I'd have no objecion to > their use. I'd use drawings, but of course that software could be helpful > too, showing things in ways other than what a drawing can show. > > 48 W > November 20th > 1600 UTC > . > Michael Ossipoff > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re:
Hi Franco-- . I like explanations that can be understood by anyone from at least pre-secondary-school. I believe that such people can understand the sundial and map-projection explanations that I'd use. . To whom would I give explanations?: Primarily to my girlfriend. She isn't interested in math, but that doeesn't mean that those explanations wouldn't be understandable to her if she's interested in them, interested in lisening to them. . I mentioned to her that our windowsill sundial would be a Cylindrical-Equatorial Dial, because it doesn't need any explanation, because it shows the Sun's position in the most direct way. She replied that she has nothing against explanation of the Horizontal-Dial, its hour-lines and declination-lines, and considers it interesting. . So the first windowsill dial here will be a Cylindrical-Equatorial Dial, followed by a Horizontal Dial. . In general, I believe that these subjects can be explained to anyone who is interested in hearing the explanation. . So I'd offer these explanations to anyone to whom I'd suggest or offer a sundial or map-projection. I like the idea of a sundial or displayed map being accompanied by a pamphlet or a page that tells its construction-formula derivation-explanation. . Some say that people aren't interested in explanations, but I suggest that, rather, they're often just resigned to things being not explainable to them. I believe that, when shown a sundial or map, they'd like it explained. . It seems to me that every park, library, museum, plaza, and other public-spaces, should have a sundial. . -- I'm not familiar with those softare products, but I'd have no objecion to their use. I'd use drawings, but of course that software could be helpful too, showing things in ways other than what a drawing can show. 48 W November 20th 1600 UTC . Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Brief explanation/derivation for Horizontal-Dial's declination-lines?
I said it backwards. For positive declination, use NEO. For negative declination, use 180 - NEO. 48 Tu November 19th 2103 Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Brief explanation/derivation for Horizontal-Dial's declination-lines?
I should mention that, when posting about the trig-at-the-dial method, I assumed a positive declination. When the declination is negative, you just use NEO instead of its supplement. 48 Tu November 19th 1534 UTC --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Brief explanation/derivation for Horizontal-Dial's declination-lines?
I've heard that dialists traditionally disregard atmospheric-refraction, when calculating sunrise an sunset times. That allows the use of spherical-trigonometry's tangent-formula, instead of the altitude-formula, a co-ordinate-transformation. But the orrery derivation of the altitude-formula seems just as easy as the derivation of spherical-trigonometry's tangent-formula. In fact, the orrery-derivations of the alt and az formulas seem, to me, easier. ...even though those formulas are larger than the tangent-formula. The tangent formula, being briefer, involves less arithmetic, but the orrery derivation of the alt and az formulas seem more naturally and easily explained. By the way, though I'd explain declination-line construction by the altitude-method, there might be advantage in calculating it by the trig-at-the-dial method. For one thing, the alt & az formulas can have subtraction, which can cause a loss of significant digits (which would only rarely matter, with today's many-digits machines). Also, if you want the measurement to be straightforward, instead of looking for the point on the hour line that's the right distance from the sub-nodus point, which isn't on the hour-lline, then you'd need to calculate the solar altitude and azimuth both. That, and the conversion to rectangular co-ordinates, and then a little work with those co-ordinates, probably amounts to a bit more arithmetic than the trig-at-the-dial method. 48 Tu Novembeer 19th 1524 UTC Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Brief explanation/derivation for Horizontal-Dial's declination-lines?
In the date at the bottom of my post, I mistakenly said "48 M, November 18th", but the correct Greenwich date of course was and is: 48 Tu November 19th Michael Ossipoff On Mon, Nov 18, 2019 at 7:42 PM Michael Ossipoff wrote: > First, an omission in my post about the trig-at-the-dial derivation: > . > I should have said that, by the definition of the cosine: > . > NE = NP/cos h. > . > -- > . > Yes, the thing is that all of the declination-line calculations and > explanations that we've discussed here require telling the person about > some other mathematical topic or method that must be applied. > . > So It's just a question of which one. > . > Dialists are familiar with the calculation of altitude and azimuth, and > often with co-ordinate transformations in general. > . > So, understandably, some dialists would find it more convenient to use > what they already use for varius other things. > . > Which would be more useful for sundials in general? > . > If the declination-lines derivation that you explain to someone is the one > that uses altitude, then the person to whom you're explaining it knows the > altitude-formula, and knows where it comes from, how it's derived. > . > What else is it used for? > . > 1. Babylonian and co-Italian Hours: > . > Well, the altitude-formula is the basis of sunrise and sunset > calculations, and so that person will also know where the Babylonian and > co-Italian hour-lines come from, how they're calculated, and from where > comes the formula by which they're calculated > . > 2. Altitude-Dials: > . > Altitude dials are the most easily-built portable dials. And they're the > most easily-used of the easily-built portable dials. > . > And the altitude-formula is their basis. > . > 3. Reclining-Declining Dials and Co-ordinate Transformations: > . > Of course the formulas for alt and az from h and dec are the general > formulas for spherical co-ordinate transformations. > . > And of course one use of co-ordinate transformations is the constructeeion > of Flat-Dials on any surface in any orientation. ...including > Reclining-Declining Dials. > . > So I'd say that the person you're explaining declination-line construction > to gets a lot of other sundial-useful appications with the altitude formula > alone, and moreso with the altitude and azimuth formulas. Of course the > azimuth-formula's orrery derivation is very similar to that of the > altitude-formula. Explain one, and nothing in the other will be new to the > person. > . > (...other than the easily-explained matter of the quadrant of the > azimuth-answer, depending on the signs of the numerator and denominator in > the formula.) > . > [quote] > You are right that people are more familiar > with altitude and azimuth than they are with > three-dimensional coordinates BUT... > . > You wanted an explanation that was easy to > understand and when you say: > . > > For a particular day, and at an hour shown > > on the dial, calculate the Sun's altitude. > . > I think: Hey, he has introduced a whole > lot of things I don't need to know about > when considering declination lines... > . > If I want to draw the declination lines > then I don't need to know about the day, > or the hour or the altitude or (and you > haven't said this) the latitude. > [/quote] > . > For any stationary sundial, you DO need to know its latitude, regardless > of what method you use for the declination-lines. > . > The day? What's actually needed in the methods that I described isn't > really the day. It's the declination. And that's needed for any method of > drawing a declination-line. To draw a declination-line, you need to know > the declination for which you're drawing the line. > . > Yes, in my discussion, I spoke of the day. But that conversational > reference to the day wasn't intended to imply that the day was an > additional independent-variable needed in addition to the declination. > . > Of course if you want to mark the declination-lines with their > correspoinding dates, then you need to know them. ...regardless of which > declination-line method you use. > . > The hour? Do you need to know the hour? You bet you do! > . > ...just as, with your method, when you've written the equation of that > conic-section, from the interection of the cone with the plane, and you're > plotting the curve--you need to know x in order to calculate y. > . > With the analytic-geometry method, or the altitude-method, or the > trig-at-the-dial method...with any of the methods we've discussed, it > ultimately comes to calculation of a distance from an independent-variabe. > ...such as h or x. >
Re: Brief explanation/derivation for Horizontal-Dial's declination-lines?
ir own advantages. . I was just telling some advangtages of the altitude method, or the alt & az method. . Undeniably 3-dimensional analytic-geometry is fun. I once had need for it, because it's a good way to show why, on a Steregraphic map, any circle on the globe maps to a circle on the map. . Regarding which declination-construction derivation-explanation one uses: It's a matter of of which math-topic you introduce someone to, and I emphasize the matter how useful it will be in other sundial topics. I don't mean any criticism of other construction-explanation. Of course there can be any of various considerations, suggesting any of the various methods. . 48 M November 18th 0037 UTC . Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Brief explanation/derivation for Horizontal-Dial's declination-lines?
Oh alright, here's the derivation by plane trig at the dial: . .First, of course this is what gives the natural and easily-explained derivation for a Horizontal-Dial's hour-lines, and so I'll show that first: . I'll designate lines by the letter-names of their two endpoints. . When I state a sequence of three points' letter-names, I'm referring to the angle that they define. . If I want to refer to the triangle that they define, then I'll precede them with the word "triangle". . The following letters will stand for the following points: . N is the nodus. . P is the point where the shortest line from N, perpendicular to ON intersects the ground. . E is the nodus's shadow at the equinox, at the hour of interest (h/15). . D is the nodus's shadow at the declination on the date of interest (dec) at h/15. . O is the origin and intersection of the hour-lines. . Say that, at N, on the polar axis ON, there is mounted a Disk-Equatorial Dial. . NP, that dial's noon-line, has a length of OP sin lat. If that dial's hour-line for hour h/15 is extended to the ground, it extends to E. . PE = NP tan h = OP sin lat tan h. . PE/OP = tan POE (the angle on the dial for the hour-line for hour h/15). . That straighforwardly demonstrates the construction of an hour-line of a Horizontal-Dial, based on a disk-equatorial dial. . Now, for the position of D: . Regarding the triangle NEO: . OE can be gotten as OP/cos POE. . ...or as sqr( OP^2 + PE^2). . NEO = asin(ON/OE). . ...or, if you prefer, = acos(NE/OE) ...or ATAN(ON/NE) . NED = 180 - NEO, because D and O are points on the same line, on opposite sides of E. . So you have NE, NED, and END (the declination, a given quantity). . So you have ASA (angle-side-angle) . So you can solve triangle NDE for DE, by the Law of Sines. . So, measure distance DE, along the hour-line for h, to mark the point on the declination-line for the date of interest. . --- . But I'd rather give the Horizontal-Dial declination-line derivation that uses the Sun's altitude. It seems to me that the orrery derivation of the altitude-formula is easier and clearer to explain than the above trig-at-the-dial derivation for a point on the declination-line. . ...and that someone who'd like a derivation for the Horizontal-Dial's declination-lines, is going to later more likely have use or need for altitude (or terrestrial-distance) or azimuth calculations, than for other trig problems or other 3-dimensional analytic-geometry problems. . 47 Su November 17th 2140 UTC . Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Brief explanation/derivation for Horizontal-Dial's declination-lines?
When I listed trig, in my previous message, I was referring to the fact that there's a 3rd derivation-approach that applies plane trig at the dial itself (but of course not just on the horizontal-plane). With any one of those 3 derivation-approaches, it would be necessary to explain either some 3-dimensional analytic-geometry; or the derivation of at least the formula for altitude (or maybe azimuth too) from h and dec; or trig for the solving of triangles. The trig needed for deriving the altitude and azimuth formulas consists only of direct use of the definitions of the trig functions, whereas the trig-at-the-dial derivation involves several plane triangles, and the solution of a non-right triangle...meaning that the person you're explaining to would have to hear about more trig than that required for deriving the altitude-formula. The altitude and azimuth formulas can be directly and straighforwardly derived by applying the definitions of the trig functions to an orrery. ...for a brief and straightforward derivation that would make sense to anyone with no prior experience in the subject. On Sun, Nov 17, 2019 at 1:42 PM Michael Ossipoff wrote: > I mean, when you're choosing which declination-lines > construction-explanation to use, there's the matter of: Which of the > following is that person more likely to have occasion to use? Or which is > more likely to be of interest and use to someone interested in sundials or > astonomical matters?: > > Altitudes (or terrestrial distances) and azimuths? > > 3-dimensional analytic geometry > > trig > > 3-dimensional analytic geometry and trig are of course useful for many > things. But celestial altitudes and azimuths, and terrestrial distances, > are of frequent and direct use and interest to people interested in > sundials or astronomical matters. > > So that's why I'd give the altitude &/or azimuth explanation for > declination-line construction. > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Brief explanation/derivation for Horizontal-Dial's declination-lines?
Frank-- . As you described, a Horizontal-Dials' (or any Flat-Dial's) declination-lines can be constructed, by 3-dimensional analytic geometry, as the intersection of a cone with a plane. . Here's another way: . 1. For a particular day, and at an hour shown on the dial, calclate the Sun's altitude. . 2. From that altitude can be calculated the nodus-shadow's distance of the nodus's shadow from the sub-nodus point. ...by dividing the height of the nodus by the tangent of the Sun's altitude. . 3. Measuring from the sub-nodus point, mark the point on that hour's hour-line at the above-calculated distance. . - . But maybe you'd rather just measure the distance from the hour-lines' intersection-point. In that case: . 1. Calculate both the Sun's altitude and azimuth at a particular date and time. . 2. As above, from that altitude can be calculated the nodus-shadow's distance from the sub-nodus point. That and the azimuth give you polar co-ordinates of the nodus-shadow with respect to the sub-nodus point. . 3. Convert the polar co-ordinates to rectangular co-ordinates with respect to the sub-noduc point. . 4. Add to the north-south co-ordinate the distance between the sub-nodus point and the hour-lines' intersection point. Then you have the rectangular co-ordinates of the nodus-shadow with respect to the hour-lines' intersection point. . 5. Convert the rectangular co-ordinates to polar co-ordinates, and mark the appropriate hour-line at the distance in those polar co-ordinates. . Or, alternatively: . 4. Divide the east-west co-ordinate by the north-south co-ordinate. . 5. Multiply that result by the distance between the sub-nodus point and the north edge of the dial or the construction-page. Mark that distance along that north-edge, from the dial's north-south axis. . 6. From the rectangular-co-ordinates, calculate the nodus-shadow's distance from the sub-nodus point. Measure that distance along the line to the point that you marked on the north-edge. . . So, there's the analytical-geometry solution that you described, and these various ways of doing it via calculation of the Sun's altitude, and maybe azimuth. . And those aren't the only derivations either. . Of all the derivations that I'm aware of, I prefer the altitude or altitude & azimuth, approach, because those calculations are of interest and use for various other matters, for sundials and all sorts of things. . . 47 Su November 17th 1830 UTC . Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Brief explanation/derivation for Horizontal-Dial's declination-lines?
Hi Frank-- Thanks for the thorough and complete explanation about conic-sections for declination-lines for flat-dials. Yes, but I want to be able to explain the actual numerical calculation of the declination-lines to someone. ...to explain the derivation of the actual formulas for the hour-lines and declination-lines. The Horizontal-Dial's hour-lines are easily and briefly explained, but I don't know of as easy an explanation for its declination-lines. I like what you said, but it would mean explaining 3-dimensional analytic geometry to someone, if you wanted two tell them exactly how the line-forumulas are derived. ...not that the other derivations are any easier. But thanks for a remarkably clear, thorough and complete description and explanation of the conic-section nature of the declination-lines for a Flat-Dial. Equatorial Dials (disk, band, or cylinder) are of course the one whose hour and declination-lines don't need explanation (well maybe a tiny bit for the declination lines--but minimal). Next is the Polar-Dial, and then maybe the Tube-Dial. But a Horizontal-Dial, while the most easily-built stationary-dial, has difficultly-explained declination-lines, if you want to tell someone in detail the derivation of the formulas. If you don't use declination-lines, or are willing to not explain them, then a Horizontal iBsut my favsorite is the Cylinder-Equatorial. . . On Sat, Nov 16, 2019 at 3:54 AM Frank King wrote: > Dear Michael, > > You ask: > > > Is there an easy explanation/derivation for the solar-declination lines > on a Horizontal-Dial? > > Yes. Here is the thought process: > > 1. You start with a plane and a point (the point must not be in the > plane) > > 2. Call the plane the 'dial plate' and call the point the 'nodus'. > > 3. Imagine a line drawn from the sun to the nodus. > > 4. Observe that, during a solar day, the line sweeps out a cone. (The > line is a generator.) > > 5. The extension of the line from the sun through the nodus sweeps out a > mirror-cone. > > 6. The common vertex of both cones is the nodus. > > 7. The common axis of both cones is polar oriented. > > 8. The intersection of the mirror cone and the plane dial plate is a > conic section. > > 9. This conic section is the required constant-declination line. > > At this stage, I have made no assumptions about the orientation of the > dial plate or the solar declination but there is an implicit assumption > that the plane and nodus are rigidly attached to the Earth. > > My nine points are best understood by considering some examples: > > EXAMPLE I – The dial plate is parallel to the Earth's equator and the > nodus is on the north side. > > [This is an equatorial dial and applies with a horizontal dial at the > north pole or a vertical direct-north-facing dial at the equator.] > > If the declination is positive, then the intersection of the mirror cone > and the dial plate is a circle whose radius increases as the declination > decreases. This circle is the constant-declination line for the assumed > declination. > > If the declination is zero, the cone and the mirror cone both degenerate > into a disc which is parallel to the dial plate so there is no > intersection. If the declination is negative, then the mirror cone is > wholly on the north side of the dial plate and there is no intersection. > > EXAMPLE II – The dial plate makes an angle of 10° to the equatorial plane. > The nodus is again on the north-side. > > [This case applies with a horizontal dial at 80°N or a vertical > direct-north-facing dial at 10°N.] > > If the declination is greater than 10°, then the sun will always be on the > north side of the dial plate and the intersection of the mirror cone and > the dial plate is an ellipse. This ellipse is the constant-declination > line for the assumed declination. > > If the declination is 10°, the ellipse becomes a parabola. If the > declination is less than 10° (but greater than −10°) then the intersection > is a hyperbola. If the declination is less than −10°, then the mirror cone > is wholly on the north side of the dial plate and there is no intersection. > > EXAMPLE III – The dial plate makes an angle of greater than 23.4° to the > equatorial plane. > > [In the northern hemisphere, this case applies with a horizontal dial > outside the arctic regions and a vertical direct-north-facing dial north of > the Tropic of Cancer.] > > Here, whatever the declination, both the cone and the mirror-cone > intersect the dial plate and the intersection of the mirror cone and the > dial plate is always a hyperbola. > > GENERAL NOTE > > Whatever the orientation of the target plane there will be some location > on the planet where this orientation is the local horizontal. The > declination lines, for that horizontal case, are precisely the declinations > required for the target plane. > > PRIVATE RANT > > Teaching geometry in schools seems to have gone out of fashion in most of > the world. In my
Re: Brief explanation/derivation for Horizontal-Dial's declination-lines?
I'll check it out. I suspect that there's no way that the declination-lines for a Horizontal Dial can be anything like as brief as that for the Polar and Tube Dials, because the horizontal surface, though convenient for building the dial, lacks any of the orientation-convenience of the Polar and Tube Dials. 47 F November 15th 1714 UTC On Fri, Nov 15, 2019 at 11:33 AM Simon Wheaton Smith < illustratingshad...@gmail.com> wrote: > My book, Illustrating Time's Shadow, is now free on.. > > www.illustratingshadows.com > > And covers hDial declination lines, and several ways of drawing them. > > Simon > > > On Fri, Nov 15, 2019, 07:49 Michael Ossipoff wrote: > >> >> Is there an easy explanation/derivation for the solar-declination lines >> on a Horizontal-Dial? I mean, easiness comparable to that of the >> declination-lines for a Polar-Dial or a Tube-Dial (Circumference-Aperature >> Cylindrical-Equatorial Dial)? >> . >> The explanation for the Horizontal-Dial's hour-lines is brief enough, but >> its declination-lines seem to need a considerably longer explanation. >> . >> I ask that because, to offer or suggest a sundial or map-projection, or >> to set up a sundial for others, I prefer one that's easy to explain. It >> seems to me that people would like something better if it can be explained >> to them, preferably without their having to listen to an long explanation. >> . >> Week 47, Friday >> November 15th >> 1450 UTC >> . >> Michael Ossipoff >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Brief explanation/derivation for Horizontal-Dial's declination-lines?
Is there an easy explanation/derivation for the solar-declination lines on a Horizontal-Dial? I mean, easiness comparable to that of the declination-lines for a Polar-Dial or a Tube-Dial (Circumference-Aperature Cylindrical-Equatorial Dial)? . The explanation for the Horizontal-Dial's hour-lines is brief enough, but its declination-lines seem to need a considerably longer explanation. . I ask that because, to offer or suggest a sundial or map-projection, or to set up a sundial for others, I prefer one that's easy to explain. It seems to me that people would like something better if it can be explained to them, preferably without their having to listen to an long explanation. . Week 47, Friday November 15th 1450 UTC . Michael Ossipoff --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Equinoctial Puzzle
...and it seems to me that the South-Solstice of 2017 occurred on December 21.686, where the time of day is expressed as a fraction of a day, appended to the date. Michael Ossipoff 41 F On Fri, Oct 4, 2019 at 7:15 PM Michael Ossipoff wrote: > Autumn doesn't begin at the autumnal equinox. The terrestrial seasons and > the astronomical-quarters are entirely different things. The > astronomical-quarters begin at the equinoxes and solstices. The terrestrial > seasons are terrestrial, though of course they're caused by, and lag > behind, the Solar-declination. The lag-time is different at different > locations, and perceptions about winter, spring, summer and autumn are > subjective, and differ geographically because of differing time-lag and > naturally-later arrival of perceived spring or summer in colder places, etc. > > No one believes that winter north of the equator really doesn't begin > until December 21st. > > The Sun is the physical origin of the Earth and its life, and the source > of the energy for life on Earth, and the cause of the seasons, but the > seasons don't begin on the astronomical-quarters. > > Michael Ossipoff > 41 F (South-Solstice WeekDate Calendar) > > ...Friday of the 41st week of the calendar-year that began on the Monday > that started closest to the South-Solstice (Winter-Solstice north of the > equator). > > ...or closest to the *approximated* South-Solstice based on the > assumption that a South-Solstice occurs exactly every 365.2425 days, > starting from the actual South-Solstice of 2017. > > The 365.2425 is from a determination that I once made of the average > length of the South-Solstice tropical-year, from 2000 to 2050. The fact > that 365.2425 is also the length of the Gregorian mean-year is coincidental. > > > > > On Fri, Oct 4, 2019 at 8:59 AM Frank King wrote: > >> Dear Hervé, >> >> Congratulations on your comments on my >> puzzle about the September Equinox last >> month... >> >> > It seems that the answer to your question >> > can be found in the attached picture >> > inclosed in a recent information letter >> > issued by the French IMCCE institute >> > specialised in celestial mechanics and >> > ephemerides calculations >> >> This gives us three times of interest on >> 23 September 2009: >> >> 07:49:51.80 Right Ascension = 12h >> >> 07:50:11.81 Solar Longitude = 180 >> >> 07:50:15.58 Solar Declination = 0 >> >> Call this the FRENCH solution. >> >> If you have an Android cell 'phone you >> can look at Sol et Umbra which gives >> these times on 23 September 2009: >> >> 07:49:49.40 Solar Declination = 0 >> >> 07:50:09.25 Solar Longitude = 180 >> >> 07:50:32.50 Right Ascension = 12h >> >> Note that the events occur in reverse >> order! Call this the ITALIAN solution. >> >> Now use the JPL Horizons program: >> >> https://ssd.jpl.nasa.gov/horizons.cgi >> >> I don't have a proper computer at the >> moment but here are three values I found >> (using my 'phone) for the single time: >> >> 23 September 2019 07:50:12.00 >> >>Solar Declination = 00:06:13.3 >> >>Solar Longitude = 180.0019964 >> >>Right Ascension = 11:59:01.94 >> >> The declination has not yet dropped to >> zero. >> >> The longitude has gone past 180. >> >> The Right Ascension has not yet >> reached 12h. >> >> Call this the U.S. solution. >> >> Moral: never believe a single source >> of information :-) >> >> If you think you can see the pattern, >> try using the Horizons program to >> investigate the March Equinox in >> 1718. Using the Gregorian Calendar, >> we find: >> >> The Right Ascension went to zero >> late on 16 March (just before >> midnight). >> >> The declination went through zero >> about the same time on 16 March. >> >> The solar longitude reached zero >> on 21 March. FIVE DAYS LATER!!! >> >> So you see: there is still a little >> bit more of my puzzle to unravel!! >> >> Very best wishes >> Frank >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Sundial designs against vandalism
I like the pond suggestion, It hadn't occurred to me, and I hadn't heard it before. Michael Ossipoff 40 F September 27th 1101 UTC --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Sundial designs against vandalism
Of course a steel gnomon securely fastened would be harder to break off. Of course you already know that people have suggested high-mounted vertical wall-dials. Of course, for those, for security, you wouldn't want one of those horizontal nodus-sticks. You'd want the usual downward-slanted gnomon. We hear the good suggestion of the vandal-proofness of an analemmatic dial, but I prefer a dial whose construction-principle can be easily explained to anyone. You wouldn't want to try to explain the analemmatic's construction to anyone other than at least a very-interested secondary-school or pre-secondary-school student. Any non-declining flat-dial's construction-principle is easily-explained. That includes a horizontal dial, an equatorial-dial, a north or south vertical dial, or a north or south reclining (but not declining) dial. In fact, it should be mentioned that even a vertical-declining dial's hour-line construction can be derived and explained without spherical trig or spherical co-oridinate transformations. (...though declination-lines for it would still require them). Michael Ossipoff Week 40, Friday September 27th 1050 UTC On Thu, Sep 26, 2019 at 4:00 AM Dan-George Uza wrote: > Hello, > > Horizontal sundials are often victims of vandalism. I am looking for ideas > or designs of gnomons which are not that easy to break off i.e. how to > attach them permanently to the base plate. Can you help? > > Thanks, > > -- > Dan-George Uza > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: What accuracy to aim for with a carefully made sundial?
Patrick-- That isn't necesary, because sundials are for telling solar time, not clock time. If you want Standard-Time, then a conversion table, incorporating EqT & longitude-adjustment, can be used. Michael Osslipoff July 31st Week 32, Wednesday 0540 UTC On Tue, Jul 30, 2019 at 3:17 PM Patrick Vyvyan wrote: > A basic problem with the accuracy of sundials is the Analemma. Due to the > tilt of the Earth, the position of the shadow for a given time moves in a > "figure-of-eight" shape over the course of the year. Therefore, even if the > sundial is very accurately marked and positioned, the shadow will only fall > exactly on the hour line twice a year - the winter and summer solstices. > > The figure-of eight Analemma is quite often marked for midday (and can > serve to give the date as well). On large sundials, the Analemma may also > be marked for every hour - but on a smaller dial, this can be visually very > confusing! Another solution, used on heliochronometers, is to allow the > dial to rotate against a scale marked with the appropriate Analemma offsets > according to the date. > > Best wishes, > Patrick > > On Tue, 30 Jul 2019 at 14:40, wrote: > >> Hi Steve, >> >> as I built a large one (https://Kepleruhr.eu with 240m²) and thought some >> about getting as accurate as possible here are my readings so far: >> >> 1) If you go for a sharp edge you will find out that the penumbra is all >> the >> times about 2 min in width which is the wandering time of all of the sun >> diameter: The sun diameter is roughly 0.5° in the sky and it takes >> roughly 2 >> min for the sun to move this angle. The penumbra in angle does not depend >> on >> the distance from the gnomon to the face. So I would suggest that the >> reading would be +/-2 min for untrained and about +/-1 min for trained >> observers. This is valid for sundials using the bypassing shadow of the >> Gnomon or the moving flare of any rectangle or circular iris. >> >> 2) I estimate a reading accuracy of the Kepleruhr by +/-15 sec (at high >> noon >> only): There is a wandering flare of 2 cm (+/- penumbra) with two side >> edges >> on a line of 2 cm which increases the reading accuracy. This wandering >> flare >> is produced by a spherical Nodus with this 2 cm gap southwards. There are >> some movies at the concerning YouTube-channel (links given at the >> website). >> >> 3) In my case I made the calibration of the sundial by >>a) calculate the hour and day line positioning by given parameters >> (declination, geometry of gnomon, Nodus, wall) >>b) erect the gnomon to the wall firstly without the painting >>c) observe the shadow at one of the next fully sunny days - taking >> series >> of photos, calibrate them with respect to lens distortions, positioning, >> etc >>d) find the hourly shadow positions by machine vision techniques >>e) adjust the above given parameter set as long as the total error of >> deviations between the calculated and measured positions got a minimum >>f) calculate the lines with the latest parameter set and do the >> painting. >>g) BINGO - it turned out (observing the sundial since years) that the >> lines correctly follow the shadow on time. >> >> 4) I am on to build a sundial with a second reading of high noon - and did >> do the concerning presentations (theory, fulfilled and planned >> implementation steps) at sundial conferences in Austria. >> >> Good luck! >> Kurt >> >> -Ursprüngliche Nachricht- >> Von: sundial [mailto:sundial-boun...@uni-koeln.de] Im Auftrag von Steve >> Lelievre >> Gesendet: Dienstag, 30. Juli 2019 19:38 >> An: Sundial List >> Betreff: What accuracy to aim for with a carefully made sundial? >> >> Hello everyone, >> >> I'm planning to make a small vertical west dial, about 1m for the width of >> the dial face, at my latitude of 49N. It will not use a nodus. >> >> The angular width of the sun makes it hard to get a really accurate time >> reading, but there will also be small errors from mis-positioning of the >> dial plate when installing (declination and inclination), imprecise >> positioning of the gnomon or the hour lines, and perhaps other causes too. >> >> First, questions directed at those of you who have practical experience of >> creating vertical sundials: If I'm careful and have a well-machined >> gnomon, >> what level of accuracy might be achievable in practice? I assume >> +/- 5 minutes throughout the day and year is fairly easy to achieve, but >> what about +/- 2 minutes, or even +/- 1 minute? How well did you do? How >> did >> you measure your wall's declination? >> >> Second, have there been any studies of how well dial users compensate for >> a >> penumbra - by which I mean gathering data from volunteers, studying the >> spread of errors in time readings taken from a dial versus a reference >> time >> source? (without employing a shadow sharpener) >> >> Thanks, >> >> Steve >> >> >> >> --- >>
Re: Orologi Solari n. 18
Sorry--I don't like to have to send corrections. But I miswrote today's date in my alternative calendar (South-Solstice WeekDate). I wrote "20 Th", but it's actually 20 F. ...Friday of the 20th week of the calendar-year that started with the Monday that started closest to the South-Solstice. ...or closest to the approximate South-Solstice based on the assuimption that there's a South-Solstice exactly every 365.2425 days, starting from the actual South-Solstice of 2017. One thing that I like about a WeekDate calendar is that the date is more obvious. It's been week 20 for some days now, and so it's obvious enough that it's week 20 today. And it's obviously Friday. ...but even as easy as WeekDate is, I managed to get today's day-of-the-week wrong. Michael Ossipoff 20 F On Fri, May 10, 2019 at 10:14 AM Michael Ossipoff wrote: > > Regarding Cone Aperture-Dials: > > I like tube-dials. (Cylindrical Circumference-Aperature Dials). They'd be > my favorite south windowsill-dial, if they were easier to mount. That's > their drawback for me. Their mounting requires orientation-exactitude in 3 > axes. Making the dial is easy enough, but mounting it is a bit of work, > especially since the mount has to be strong enough to support the tube. It > gives me more appreciation for the more easily built and mounted > Flat-Dials. No wonder they're the favorite stationary dials. They're my > favorite stationary-dials too. > > I considered an Aperture-Dial in the form of a cone. The inside is more > easily visible. But the drawing of the hour-lines would be considerably > more complicated than they'd be with a cylinder. To me that rules them out, > because I like sundials whose construction can be easily explained. I > wouldn't be inclined to set up a windosill sundial whose construction I > couldn't explain to my girlfriend, > > Michael Ossipoff > 20 Th (May 10th) > 1414 UTC > > On Tue, May 7, 2019 at 1:57 PM Gian Casalegno > wrote: > >> Dear friends, >> a new issue of the Italian magazine Orologi Solari is available for >> download from the usual site http://www.orologisolari.eu/. >> >> Here is the list of articles together with a short abstract: >> >> 1. "A sundial made inside a cone" by Aironi John >> We describe a sundial drawn inside a hollow cone, with a slit and a >> gnomonic hole on a generatrix. Sunlight penetrating inside the cone through >> a slit projects on the inner surface of the cone a light strip indicating >> the time. The formulas for tracing hour lines and calendar lines are shown. >> >> 2. "Ancient hour circles on the sphere are not maximum circles. Clavio's >> demonstration with AutocadLT." by Albéri Auber Paolo >> Cristoforo Clavio, after a long discussion with his colleagues, finally >> offered a demonstration that the maximum circle of ancient time relative to >> two antisymmetric declination circles is different for each pair of chosen >> declination circles, that is to say that the hour lines relative to the >> ancient hour are not maximum circles. Here we propose a simplified >> demonstration with images taken from AutocadLT geometric constructions. >> >> 3. "Small composite sundials" by Anselmi Riccardo >> The author presents a model of a gnomonic hole dial made with an ice >> cream container. In particular two specimens are shown and described >> declining respectively to the south and to the west. >> >> 4. "The millstone of time" by Baggio Francesco >> This article describes a horizontal mobile gnomon sundial already >> manufactured and registered in Sundial Atlas with the code IT013689. >> Project steps are explained and possible variants are proposed. >> >> 5. "An app for dialists… aspirant clockmakers" by Casalegno Gianpiero >> The author describes an Android app that simulates some famous tower >> clocks. The main features are described trying to underline the most >> interesting aspects for a gnomonist. >> >> 6. "Definition of the orientation of a flat wall" by Caviglia Francesco >> The definitions used by gnomonists for the parameters that specify the >> orientation of a flat wall (gnomonic declination and inclination or slope) >> are here discussed. Unambiguous and suitable operational definitions are >> provided and some proposals are advanced. >> >> 7. "A reflection behind the other: the double-mirror" by Ferro Milone >> Francesco >> Double-reflection geographic sundials are realized by using >> double-mirrors. The project is carried out with the help of a dynamic >> software (Geogebra), a geographical one (GMT) and a gnomonic one (Orolog
Re: Orologi Solari n. 18
Regarding Cone Aperture-Dials: I like tube-dials. (Cylindrical Circumference-Aperature Dials). They'd be my favorite south windowsill-dial, if they were easier to mount. That's their drawback for me. Their mounting requires orientation-exactitude in 3 axes. Making the dial is easy enough, but mounting it is a bit of work, especially since the mount has to be strong enough to support the tube. It gives me more appreciation for the more easily built and mounted Flat-Dials. No wonder they're the favorite stationary dials. They're my favorite stationary-dials too. I considered an Aperture-Dial in the form of a cone. The inside is more easily visible. But the drawing of the hour-lines would be considerably more complicated than they'd be with a cylinder. To me that rules them out, because I like sundials whose construction can be easily explained. I wouldn't be inclined to set up a windosill sundial whose construction I couldn't explain to my girlfriend, Michael Ossipoff 20 Th (May 10th) 1414 UTC On Tue, May 7, 2019 at 1:57 PM Gian Casalegno wrote: > Dear friends, > a new issue of the Italian magazine Orologi Solari is available for > download from the usual site http://www.orologisolari.eu/. > > Here is the list of articles together with a short abstract: > > 1. "A sundial made inside a cone" by Aironi John > We describe a sundial drawn inside a hollow cone, with a slit and a > gnomonic hole on a generatrix. Sunlight penetrating inside the cone through > a slit projects on the inner surface of the cone a light strip indicating > the time. The formulas for tracing hour lines and calendar lines are shown. > > 2. "Ancient hour circles on the sphere are not maximum circles. Clavio's > demonstration with AutocadLT." by Albéri Auber Paolo > Cristoforo Clavio, after a long discussion with his colleagues, finally > offered a demonstration that the maximum circle of ancient time relative to > two antisymmetric declination circles is different for each pair of chosen > declination circles, that is to say that the hour lines relative to the > ancient hour are not maximum circles. Here we propose a simplified > demonstration with images taken from AutocadLT geometric constructions. > > 3. "Small composite sundials" by Anselmi Riccardo > The author presents a model of a gnomonic hole dial made with an ice cream > container. In particular two specimens are shown and described declining > respectively to the south and to the west. > > 4. "The millstone of time" by Baggio Francesco > This article describes a horizontal mobile gnomon sundial already > manufactured and registered in Sundial Atlas with the code IT013689. > Project steps are explained and possible variants are proposed. > > 5. "An app for dialists… aspirant clockmakers" by Casalegno Gianpiero > The author describes an Android app that simulates some famous tower > clocks. The main features are described trying to underline the most > interesting aspects for a gnomonist. > > 6. "Definition of the orientation of a flat wall" by Caviglia Francesco > The definitions used by gnomonists for the parameters that specify the > orientation of a flat wall (gnomonic declination and inclination or slope) > are here discussed. Unambiguous and suitable operational definitions are > provided and some proposals are advanced. > > 7. "A reflection behind the other: the double-mirror" by Ferro Milone > Francesco > Double-reflection geographic sundials are realized by using > double-mirrors. The project is carried out with the help of a dynamic > software (Geogebra), a geographical one (GMT) and a gnomonic one (Orologi > Solari by Gianpiero Casalegno). Three computing examples and a project > image terminate the article. > > 8. "And before Foster ?" by Gunella Alessandro > The author wants to remind the reader that the use of "rulers" in the > construction of sundials, a method generally attributed to Samuel Foster, > was actually already proposed in the previous century. In particular an > instrument is shown as already described by Clavius and probably of > Germanic origin. > > 9. "The analemma and the Cathedral of Majorca" by Pol i Llompart Josep > Lluís, Ruiz-Aguilera Daniel > The authors describe the cathedral of Majorca and explain how they made > the photos of the solar analmma above the "cathedral of light". > > 10. "A Roman portable watch" by Quadri Ulisse > The author describes the use and the principle of operation of a portable > solar clock from the Roman era, kept at the Museum of the History of > Science in Oxford and of which he made a copy in brass and steel. > > A digital bonus can also be downloaded for additional reference material. &g
Re:
Hi Mario— . Thanks for pointing that out—I didn’t know that “tempora” meant “seasons” in Latin. I knew that “tempus” meant “time”, but I didn’t know about the specific seasonal meaning. . In English, “temporal” just means “of or pertaining to time”, but you point out that it used to mean “seasonal” . So then I now realize that “temporal hours” isn’t incorrect, but is just different from what that word means in English. . Thanks again for clarifying that. -- Dan— . I want to emphasize that I wasn’t criticizing any word-usage of yours. I was just objecting to the word-usage in the text that you were quoting (a usage that has justification that I didn’t know about). - Michael Ossipoff 20 M 1546 UTC --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Temporal hours to modern hours
That sounds like just a conversion between two ways of naming the equal-hours. ...converting between the.modern 12-hour naming, and a numbering that calls the hour from 6 a.m. to 7 a.m. the 1st hour. It doesn't take into account the different lengths of the hours, which depend on the varying length of the day, because the sunrise-sunset day is divided into 12 equal parts (as is the sunset-sunrise night). I don't agree with the term "temporal hours". The first book that I found that mentioned seasonal-hours called them "*temporary hours*". That name makes sense, because the length of an hour is temporary instead of constant, because it varies with the season. "Temporal hours" doesn't make sense, because all hours are temporal. "Temporal" just means "of, about or pertaining to time". Maybe a good term would be "seasonal-hours", because their length varies seasonally. One way to get temporary-hours is from Babylonian and co-Italian hours. Divide the Babylonian hour from the sum of the Babylonian hour and the co-Italian hour. Michael Ossipoff 19 Th (Thursday of the 19th week of the calendar-year that started with the Monday that started closest to the South-Solstice. ...or closest to the approximation to the South-Solstice, based on the assumption that a South-Solstice occurs exactly every 365.2422 days, starting from the actual South-Solstice of 2017). (The South-Sostice of 2017 occurred at December 21.686...where the time of day is expressed as a fraction of the day from midnight of that day.) ... On Thu, May 2, 2019 at 5:05 PM Dan-George Uza wrote: > Hello, > > In a note quoted below from the "Dictionary of Greek and Roman > Antiquities, John Murray, London, 1875" I found the following advice to > convert temporal hours to modern hours. > > *"A very quick and easy rule of thumb, when we read "the third hour, the > sixth hour", etc., is to add 3, 6, etc. to 5:00 A.M.: The first hour, for > example, runs from roughly 6 to roughly 7 A.M.; and the ninth hour from > roughly 2 to roughly 3 P.M."* > > Source: > http://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA*/Hora.html > > Of course back then there was no summer time either... > > But is there a closer aproximation for this, perhaps using a simple > mathematical formula? Are there apps that can convert temporal hours > directly to modern equivalents, perhaps as a spreadsheet? > > Dan Uza > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: Reinhold Kriegler
I too am saddened and shocked by the loss of Reinhold Kriegler. I always felt that Kriegler exemplied the *best* of what a community of dialists would be like. The most civil, civilized, inoffensive, polite, considerate, member. Those attributes stand out, aside from his impressive website with is wide coverage of dials and dialists worldwide, and his own artistically-aesthetic dials. Michael Ossipoff 14 W 0200 UTC On Wed, Mar 27, 2019 at 6:14 AM lvadillo wrote: > I'm deeply impacted by the sudden death of our friend Reinhold. Met him 10 > years ago and since then we kept a good relationship and a constant > exchange of information, from him always positive and very helpful. A great > loss for the gnomonic community, will miss him forever, a real friend of > great humanity. > My sincere condolences to family and relatives. Rest in peace. > > Luis E. Vadillo (in name of myself and the spanish gnomonic association > AARS) > Spain > > >> -- Forwarded message -- >> From: "Martha A. Villegas V." >> To: sundial@uni-koeln.de >> Cc: >> Bcc: >> Date: Tue, 26 Mar 2019 05:43:51 + (UTC) >> Subject: Our sundial friend Reinhold Kriegler >> Sundial friends, >> >> Reinhold Kriegler had many contributions to the gnomonic field, I am sure >> many of you had the chance to be in contact with him. >> With deep sadness I want to communicate that my dear friend Reinhold >> passed away on Saturday 23th in Dessau. >> >> His rich web http://www.ta-dip.de is still working; you can find a lot >> of interesting information on it. >> >> Rest in peace. >> >> Greetings to all of you >> >> Martha A. Villegas (from Mexico) >> >> >> --- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re:
> > On 23 Mar 2019, at 15:51, Michael Ossipoff wrote: > > > > > The International Standards Organization WeekDate calendar (ISO > > WeekDate > > Calendar): > > > > . > > > > The calendar year starts with the Monday closest to Gregorian January > > 1st. > > > > Close. No, not just close. My definition is a correct wording for a definition of ISO WeekDate. > The start of each week is defined as a Monday. The first week of > the year is the first week of the calendar year that contains a > Thursday. > > Effectively, the same thing as you describe, but the definition makes no > reference to Monday or January 1st. > You mean that the definition *that you read* makes no reference to Monday or to January 1st. I didn't say that I was quoting the official wording, or the Wikipedia wording. I was giving a less arbitrary-sounding, clearly, naturally and obviously-motivated wording of the definition. In other words, a better wording of the definition. Michael Ossipoff 13 Sa 1958 UTC > Barry > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
