Roger-- I'm not sayings that the vertical projection isn't part of a valid explanation, and I'm not even claiming to set myself up to say that your explanation wasn't.
Now that you mention it, I've heard of sundial layout derivations using an orthographic projection. And I never found those derivations to be the ones that showed me anything, though, as I said, I don't presume to say that they aren't valid, or that yours isn't valid. ...only that I myself didn't find them helpful. So, since I perceive those explanations as more difficult, then I don't perceive them as likely to be helpful to gradeschool students. Michael Ossipoff On Tue, Jul 17, 2018 at 7:31 PM, Roger <rtbai...@telus.net> wrote: > Hi Jack and Michael, > > > > I don’t agree. The concept is very simple. Perhaps you have had bad > teachers. One of my presentations at the upcoming conference is a purely > grapghical method of designing an analemmatic sundial. No trig, not even > geometry other than the Greek’s ruler and string or a simple math set with > ruler, protractor and a compass. From this graphical technique comes a > whole new concept by Chris Lusby Taylor for seasonal makers that I will > describe at the conference next month. > > > > To demonstrate the simple concepts for analemmatic sundials, start with > this experiment as a class activity, hands on and interactive. Cut out a > circle of cardboard. Stick a pencil through the center at a right angle to > the disc. Hold it with the pencil vertical. Look straight down on the disc, > a circle true size. Hour angles drawn every 15° would also be true angles. > The pencil is seen as a point. Now physically drop the disc and pencil onto > a horizontal table. Get down to view across the table and turn the disc to > see it on edge. It will be seen as a true length straight line equal to the > diameter of the circle. The pencil will also be seen a true length line. If > you chose the right length of pencil, the pencil will make an angle to the > horizontal equal to your latitude. The disc will make an angle to the > co-latitude. Now get up and look straight down on the disc and pencil on > the table. The disc will be seen as an ellipse and the pencil as a shorter > line as neither disc or pencil are true length. Look at it straight down > from above and mark the point on the desk that is directly under the end of > the hour mark on the disk starting with the disc turned to the starting > point noon being directly under the pencil. These points define. the hour > ellipse for an analemmatic sundial. > > > > Next the enigmatic date line. Consider the sun shining down at noon at any > day of the year onto the pencil through the disc on the table. The sun > shines down on the pencil and there is a unique point on the pencil each > day where the sun at noon shines directly onto the rim of the disc. At the > summer solstice the sun is high in the sky. The angle of the suns ray down > to the disc rim is at an angle of 23.5° to the disc. At the winter solstice > the angle is -23.5 ° On the spring and fall equinox the angle is 0°. Every > day has a different angle, the solar declination for that day. Now you > could switch to ruler and protractor marking on paper right angle > triangles with the base equal to the disc radius. Measure angles from the > base point up at the chosen declination angle and draw a line at that angle > to the line at right angles to the other end of the base line for the > declination points for the chosen dates. Now draw a line for the horizon at > an angle to the disc base line equal the latitude. Draw lines perpendicular > to the horizon line to the chosen declination date points. The points on > the horizon line are the points where you stand on the analemmatic sundial. > > > > In one class activity session all the kids with a good teacher could make > their own analemmatic sundial based on these simple concepts. It involves > simple tools from the standard geometry set and a simple concept of > looking at a circular disc with a rod through the center from different > points of view. > > > > The general problem is that sundials are not on the curriculum for any > school boards. Teachers teach to the curriculum. The few teachers I have > met in NASS are excellent but there are very few others are interested in > such an extracurricular activity. Perhaps that is the value of a > analemmatic sundial installation at a school would be to stimulate interest. > > > > Regards, Roger Bailey > > Walking Shadow Designs > > > > *From: *Jack Aubert <j...@chezaubert.net> > *Sent: *July 17, 2018 6:27 AM > *To: *'Michael Ossipoff' <email9648...@gmail.com>; 'sundial list' > <sundial@uni-koeln.de> > *Subject: *RE: Is this sundial business 'genuine', or not? > > > > I very much agree with this. In fact, at the risk of sounding stupid, I > have to confess that I don’t have an intuitive grasp of how an analemmatic > dial works. Yes, I have at various times gone through the explanation, but > it does not stick in any way that I can mentally attach to the plane of the > earth’s surface and the motion of the celestial sphere. I know I could > review the geometry and remember it if I tried but agree that the > geometrical projections involved are beyond the grasp of almost all > children and almost all adults. > > > > Jack > > > > *From:* sundial <sundial-boun...@uni-koeln.de> *On Behalf Of *Michael > Ossipoff > *Sent:* Tuesday, July 17, 2018 12:29 AM > *To:* sundial list <sundial@uni-koeln.de> > *Subject:* Re: Is this sundial business 'genuine', or not? > > > > > > To continue something that I started before: > > > > The derivation of the construction of the Analemmatic could be explained > to anyone, with 3 lesson-sessions, over 3 days. > > > > Yes, an Analemmatic Dial could be educational, when it gives people > incentive to study, read about or listen to the dial's derivation, is > construction-explanation. > > > > So the Analemmatic with its trigonometry requirement, could be useful, > helpful, educational, at a highschool (secondary school), college or > university. > > > > ...but not at an elementary-school (primary school), okay? How many > elementary-school kids would want to listen to that explanation? > > > > Will someone tell me how an Analemmatic Dial would be educational at an > elementary-school? > > > > There was a line in the movie "Fatal Attraction", in which the mother is > considering taking their primary-school child with her, when she goes to > visit her father (probably for the purpose of looking at a nearby house > that they're considering purchasing). The Father questions whether the > child should miss school by going on the visit. The mother replies, "What's > she going to miss, trigonometry?" > > > > What dial's explanation would be of interest to an elementary-school > audience? Any of the Central-Gnomon Equatorial dials, such as the > Disk-Equatorial, Band-Equatorial and Cylinder-Equatorial (with central > gnomon). Their showing of Solar Time is completely direct. > > > > The Horizontal Dial's explanation is brief, and might very well be > acceptable, of interest, to many elementary-school students,. > > > > Vertical or Reclining, but non-Declining, Flat Dials might not be > significantly more difficult to explain, since they're just horizontal > dials for a different latitude. ...demonstrable with a globe. > > > > So, if some of the kids are little vandals, you could install a South > Vertical Dial, bracket-mounted high on a wall (or flat-mounted on a > south-wall). > > > > The Circumference-Aperture Cylindrical Equatorial Dial would be easier to > explain than the Analemmatic, but its explanation might still only be of > interest to highschool students. > > > > ...because of its geometric diagram, with its triangles, with > letter-labeled angles, and the equations relating its angles--and the > making of new equations by doing the same thing to both sides of an > equation, or adding or subtracting two equations, or substituting one equal > thing for another in an equation--sounds like a secondary-school topic. > > > > Well, probably pre-secondary school (junior-high, middle-school) kids too, > because when I was in junior-high, our general-math class introduced > equation-solving. > > > > ...but I don't know if there would be much interest in it in > primary-school. I don't know if I'd be brave enough to get up in front of a > class and start explaining it there. > > > > Anyway, so I'm just saying, only offer dials whose construction derivation > explanation would be of interest to the people to whom you're offering the > dial. > > > > By the way, I say the same thing about map-projections. For a first > world-map projection, for a wall or a book-page, in primary-school, I > suggest Apianus II, an elliptical pseudocylindrical map with equidistant > parallels. > > > > (A pseudocylindrical map has parallels that are mutually-parallel straight > lines, each one uniformly divided by the meridians (In other words, the > scale along each parallel is uniform.) ). > > > > The equator and central meridian have the same scale, and the map is twice > as wide as high. > > > > If that scale along the parallels is the same along each parallel, and is > the same as the uniform scale along the central meridian, that's the > Sinusoidal Projection. It's useful, but many people feel that it looks > awful. It's that roughly diamond-shaped world map that you might have > seen. Apianus II has a pleasing globe-similar elliptical shape. > > > > Michael Ossipoff > > > > > > > > > > > > > > On Thu, Jul 12, 2018 at 8:47 PM, Michael Ossipoff <email9648...@gmail.com> > wrote: > > If I may correct a small error in something that I said: > > > > I said: > > > > > > That's easily remedied by having additional apertures at the 6 am & pm > positions, with a few separate special hour-lines for use with those > aperatures. I'd make those 6-o'clock apertures double, to make them > easily-distinguished. > > > > Actually it would be at the 9 a.m. and 3 p.m. positions, measured by the > hour-lines inside the tube. ...in other words, at the points 90 degrees > from the top of the tube. > > > > The apertures at those two side-points would cast the light-spots to be > used for time at or before 6:00 a.m.,. and at or after 6:00 p.m. > > > > As with the main aperture, the hour lines for those side-apertures would > be marked so that their angular distance along the circumference from the > point opposite the aperture is twice that hour angle's time's difference > from 6 o'clock. > > > > Michael Ossipoff > > > > . > > > > > > > > > > On Thu, Jul 12, 2018 at 12:54 PM, Michael Ossipoff <email9648...@gmail.com> > wrote: > > I've just realized that I mis-spelled "aperture". I don' t know why I > added the extra "a". > > > > Michael Ossipoff > > > > On Thu, Jul 12, 2018 at 12:26 PM, Michael Ossipoff <email9648...@gmail.com> > wrote: > > > > As Hunt pointed out, there might be many locations where an Anelematic is > the only dial that won't be stolen or vandalized. And I like it. But I'd > consider it a last-resort, to be used only when a previous dial has been > stolen or vandalized. That's because I prefer sundials whose > construction-principle is easily explained to everyone. > > > > Other reasons to consider other sunndials is the Analematic's requirement > for a large flat area of land, and the greater accuracy of dials that have > their own built-in gnomon. > > > > In the Analematics favor, though, it can be said that its > construction-principle can be explained, probably in 3 lessons, on 3 > different days, to anyone who's willing to sit down and listen to the > explanation. And though the Analematic can't be called "educational" > except for people willing to listen to that explanation, it can be said, on > the positive side, that it gives people *incentive* to listen to an > explanation on that subject. > > > > So, in that regard, you could say that the Analematic could be > particularly educational. > > > > Though of course each of the kinds of sundials has its own particular > advantages and application, my general favorite stationary dial is what I > call the Tube-Dial, the Circumference-Aperature Cylindrical Equatorial > Dial. > > > > 1. Like other equatorials, it shows the time in a particularly direct way. > > > > 2. . It does need a bit more construction-principle explanation than other > equatorials, but, as with the Analematic, that makes it more educational, > by giving incentive for listening to it. > > > > 3. It uses a light-spot instead of a shadow, making it more accurate (not > indistinct). > > > > 4. Because it's a light-spot in a shaded space, it's easier to look at on > a bright sunny day. > > > > 5. Lilke other equatorials, it's easy to accurately estimate time by > linear interpolation between the lines. > > > > 6. Its light-spot moves twice as far per hour as the shadow in an > ordinarly central-gnomon equatorial dial. > > > > 7. It's easier to build than other equatorials. Just make a hole in the > side of a cylinder and mark equally-spaced lines. ...6 a.m to 6 pm, > marked all the way around the inner circumference from the top. > > > > Of course its disadvantage is that it can only be read from one position, > moreso than any other dial. > > > > As I said, all the kinds of dials have their own particular advantages and > applications, but the Tube-Dial is my favorite stationary dial. > > > > It's perfect for a south windowsill. .... and of course a south windowill > is the one that gets sunlight all year. > > > > One other disadvantage is that, with only an aperature at the top, it > won't show times before 6 a.m. or after 6 p.,. > > > > That's easily remedied by having additional aperatures at the 6 am & pm > positions, with a few separate special hour-lines for use with those > aperatures. I'd make those 6-o'clock aperatures double, to make them > easily-distinguished. > > > > For an outdoor use, it could use a big metal drum, or any ready-made > cylinder, with a hold drilled in it at the top (...and preferably a pair of > auxilliary 6 o'clock aperatures at each 6 o'clock position, with > corresponding speial extra hour-lines opposite them. > > > > Michael Ossipoff > > > > > > > > > > On Wed, Jul 11, 2018 at 5:06 AM, William Irvine < > william.irv...@fastmessage.co.uk> wrote: > > > Thanks to the people who responded, either direct to this Mailing > List - or had E-mailed to me privately, with their own comments. > > Based on those replies, I contacted "Sunclocks" to ask why their > price was so low (compared with the people acting as Distributors > for them) - as well as why they show so many 'negative' details > on their website, telling people about dangers of Human Sundials. > > > I will not give away the 'secret' here, (as you can always contact > them yourselves if you want) - but it appears that they exploit a > 'loophole' in Scottish Law, which allows them to make much greater > profits by persuading customers NOT to purchase, but seemingly it > only works if their advertised price does not go above 20 Pounds. > > Apparently, that is why their website says that the price will be > permanently FIXED at this level - and would never be increased at > any time in the future, no matter what happens to 'inflation'. > > Doug Hunt explained their overseas Distributors get customized > Plans at the same low cost, and choose their own selling prices > to suit 'local markets' - while "Sunclocks" profit from persons > who do NOT buy, so this is a "win-win" situation for everybody. > > > Because each "Sunclock" layout will automatically become its own > 'advert' (particularly those in public locations), the business > is basically guaranteed a 'chain reaction' of enquiries - plus > they make money regardless of whether any person buys, or not! > > After looking at hundereds of pictures on their website (as they > say themselves "from Australia to Alaska and Tasmania to Tibet"), > I now understand why it is such a world-wide success - and they > do not even need to supply a 'physical' product, since all sets > of customized Plans are simply 'down-loaded' via their website. > > However, as Frank King indicated in his reply, some unscrupulous > people try 're-selling' those Plans (or even making counterfeit > copies, under their own name) - but that just annoys people who > buy them, as the 'Latitude & Longitude' will be wrong so all the > measurements plus layout instructions would not apply either. > > > Many thanks, also, to those people who gave me suggestions about > various means of making an income from sundials - for example by > giving some 'lectures', as I prefer not to work in stone/metal. > > As far as my own 'paying hobby' is concerned, I might just try > painting some "Sunclocks" on school playgrounds - because other > businesses already do it, making hundreds of Pounds each time! > > > > Sincerely, > > Bill Irvine. > > > -- > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > > > > > > > >
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