Re: Spreadsheet for analemmatic sundials

[Chris Lusby.Taylor]

I used a string looped around the foci to lay out a 'human' analemmatic. I found
that the string didn't stretch noticeably and you can hold the pencil upright
well enough to get a more than adequate ellipse. Part of my goal was to lay out
the entire dial, including the date scale and compensation for my westerly
longitude, without using any measurements or calculations except for a
protractor. No spreadsheet, no tables, no calculator, not even a ruler. Just a T
square and a protractor to lay off the latitude for the eccentricity, the
longitude (1 degree) and hours (15 degrees) on a circle around the ellipse,  and
the declination (23.4 degrees) and months (30 degrees) on a circle around the
date scale.
It was a great success. If anyone wants the full details of the method, please
email me.

I thought of using a wire loop, but you'd have to use a very thin, bendy wire to
get it to bend tightly around the pencil and to get all kinks out. The thinnest
multistrand electrical cable, or something similar to what John uses for his
wire gnomons (sold for clock weight hanging), would work best, I imagine.

Chris Lusby Taylor
51.4N 1.3W

John Carmichael wrote:

> Use a wire or cable instead to avoid streching.
>
> John
>
> John L. Carmichael Jr.
> Sundial Sculptures
> 925 E. Foothills Dr.
> Tucson Arizona 85718
> USA
>
> Tel: 520-696-1709
> Email: [EMAIL PROTECTED]
> Website: <http://www.sundialsculptures.com>
> - Original Message -
> From: "Roger Bailey" <[EMAIL PROTECTED]>
> To: 
> Sent: Sunday, April 21, 2002 9:59 AM
> Subject: RE: Spreadsheet for analemmatic sundials
>
> > Hello Richard,
> >
> > This is a good suggestion. Measuring two lengths is easier in the field
> than
> > trying to measure the perpendicular distances from the two axes. The
> > distances from the center are already included in the spreadsheet as the
> > polar coordinates for the points are calculated. The distance from the
> > center is "r" in cells I25 to I45. The distance from the noon point where
> > the hour ellipse crosses the N/S axis is easily calculated from the right
> > angle triangle geometry as the square root of  x squared plus (b-y)
> squared.
> > We will consider this change to the posted version.
> >
> > Another construction aid is included in the spreadsheet, the string loop
> > length in cell G17 and the focal points "C" in cell G16. Peg the focal
> > points at +/- c on the E/W axis. Take a loop of string equal to the length
> > in cell G17 and loop it over both focal point pegs. Hold the string loop
> > taught with a pencil or chalk in the other end of the loop. Use this to
> lay
> > out the hour ellipse. This is a great guide for constructing the dial but
> > the string stretches and the pencil wobbles so this technique is not
> > accurate enough to precisely locate the points.
> >
> >
> > Roger Bailey
> > Walking Shadow Designs
> > N 51  W 115
> >
> > -Original Message-
> > From: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED] Behalf Of Richard Hollands
> > Sent: April 21, 2002 8:17 AM
> > To: sundial@rrz.uni-koeln.de
> > Subject: RE: Spreadsheet for analemmatic sundials
> >
> >
> >
> > Well I'm truly impressed with this spreadsheet though a little depressed
> by
> > it too - it's so professional.
> >
> > I have a suggestion. I've found it useful to included two extra columns
> that
> > give the distance from the hour point to the centre and to the noon point.
> > Then you can use a very simple method of construction. Put a peg in the
> > centre and noon points and attach one of those retractable steel tape
> > measures to each peg. (A loop of string round bamboo pegs works well).
> Then
> > you retract or extend the two rules, one in each hand, with them crossed
> > over in front of you while someone reads out the distances. All the hour
> > points can be very quickly marked this way.
> >
> > Cheers,
> >
> > Richard
> >
> > -
> >
> > -
> >
>
> -

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Re: Largest Sundial

[Chris Lusby.Taylor]

"Romano, Judith" wrote:

> Does anyone know what the "largest" sundial in the world is?  For some
> reason I seem to think India -- but when searching the WWW, could not find
> the answer.  Thanks!
> -

This was debated here three years ago. I think you're right that the largest
purpose-built man-made sundial is indeed at Jaipur in India. There are some
larger natural features that act as sundials, including three mountains in a
German-speaking area (Austria, perhaps, I forget?) and someone pointed out
that the whole globe is a sundial.

I recently read in The Sunday Times (a British newspaper) that the biggest
sundial in Europe is in a town in Russia. They had a picture of it.

Hope this helps
Chris Lusby Taylor
51.4N 1.3W



-

Re: About the circumpolar parabola

[Chris Lusby.Taylor]

The sundial park at Genk in Belgium has a dial where the gnomon is this
very cone. See dial number nine at .
Its edges cast shadows on the horizontal dial that it rests on. They
directly indicate Italian and Babylonian hours. Interestingly, these hour
lines are identical to the half hour lines of a horizontal dial. So, if
part of the cone were replaced by a polar gnomon the same lines could be
used to show Italian (sunset-related), Babylonian (sunrise-related) and
common (midnight/midday-related) local apparent time. They would merely
need different numbering for each time system.
Indeed, you don't need the entire conical surface - any complete section
would do. So, the cone could be reduced to an equatorial circle or, in
latitudes <45 degrees, a vertical ellipse. Thus, adding an equatorial
circle to any horizontal dial allows it to indicate Babylonian and Italian
hours, with no extra lines, but noting that every conventional hour line
represents a two hour period - so 10am should be labelled as 20:00 Italian,
11am as 22:00 Italian, 1pm as 02:00 Babylonian, 2pm as 04:00 Babylonian...
Chris Lusby Taylor
51.4N 1.3W
 
Anselmo Pérez Serrada wrote:

Hello
Fer and all,   
Thanks for the reference. I hadn't seen Fantoni's book but I have heard
that it is very good.As
I told you, I heard about that topic from somebody else. Yes,
you are right in saying that the curve can be some other conical if the
sundial reclines, but ifit
is horizontal it doesn't matter which the latitude is: the curve is a parabola
(more or less open). An
special case rises when the sundial is equatorial: the evolving curve of
the ita-bab lines isa circle;
and if we make an stereographical projection instead of a gnomonical one,
we geta nice diagram that
looks like a rose window or a ball bearing, if you prefer. Greetings, Anselmo
Perez Serrada [41.652 N  4.723 W]

- Original Message -

From:
fer j. de vries

To: sundial@rrz.uni-koeln.de

Sent: Sunday, March 17, 2002 11:30
AM

Subject: Re: About the circumpolar
parabola
 Hello Anselmo, About
the property you mention a description may be read in the Italian book
"Orologi Solari" by Girolamo Fantoni, 1988.He
describes the Babylonian and Italian hourlines and draw figures with the
"Cerchio circumpolari visibili". Have
in mind that you only get a parabola on an horizontal sundial.For
other sundials the intersection of the cone with the sundial's face will
be an ellipse or hyperbola . Best
wishes, Fer.   Fer J. de Vries
mailto:[EMAIL PROTECTED]
http://www.iae.nl/users/ferdv/
Eindhoven, Netherlands
lat.  51:30 N  long.  5:30 E
 

Re: Visiting the North Pole

[Chris Lusby.Taylor]

Hi Geoff,
It's very windy but dry here. Anthony is at : <[EMAIL PROTECTED]>
Would this be about Pilkington and Gibbs?
Best wishes
Chris
 
[EMAIL PROTECTED] wrote:
Hi Chris
I am trying to contact Anthony
Eden - do you have his e-mail address. It is raining in Brussels.
Best wishes
Geoff

Re: Visiting the North Pole

[Chris Lusby.Taylor]

Fernando Cabral wrote:

> Hi
>
> Some of the members of this list will remember that two years ago I mentioned 
> I was going to
> the Sahara Desert. I was to run the
> Marathon des Sables, a 236-km race in the Morocco.



> Now I am returning. I want to run that race again.



> This time I'll do it a little different. After the race, instead of coming 
> back to Brazil
> I'll visit the North Pole. From Morocco to Moscow, Siberia and... North Pole. 
> I expect to be
> there from the 21st to the 28th of April.
>
> Maybe I'll take with me a especially made sundial (aha, you though this had 
> nothing to do
> with sundials?). Any suggestions?
>
> - fernando
>

Fernando, you really make the most of life, don't you! Have a wonderful time.

During the day you will want a portable universal sundial - a foldable 
equatorial ring dial
would seem ideal. The smallest I have seen are sold at the Museum of the 
History of Science in
Oxford - about 25mm diameter. I would suggest you make one a bit bigger and 
mark the latitudes
of Morocco, Moscow and, of course, the North Pole on it for ease of setting. At 
the North Pole
it will confirm the date and show lines of longitude if you know the time, or 
vice versa.

During the night I suggest you should use a nocturnal. They are universal as 
far as latitude
is concerned and tell you local mean time if you know your longitude. No 
equation of time
correction needed!
If you had space, I would suggest you also take an astrolabe, but they are 
rather bulky.

Keep us informed.

Chris Lusby Taylor
51.4N 1.3W




-

Star finder (astrolabe) for sale

[Chris Lusby.Taylor]

I'd like to draw your attention to a star finder for sale on the
Internet auction house eBay. See


I own one of these, though I have to confess I haven't looked after it
well and it is now missing some of the transparent overlays :-(

I find it interesting that aircrew were issued with astrolabes, for
that's what it is, during the Second World War. Strictly, perhaps, it
isn't an astrolabe in that it has no alidade and no scales on the
reverse, and the projection isn't stereographic. The instructions show
how you can identify stars if you select and set the overlay
corresponding to your Dead Reckoning (calculated/assumed) position. They
don't tell you how to improve on dead reckoning by observing the stars'
actual positions, but that must surely have been the intent.

Chris Lusby Taylor
51.3N, 1.4W

-

Re: Nocturnals; longitude adjustment

[Chris Lusby.Taylor]

"R.H. van Gent" wrote:

> > Ania Marczyk wrote:
>
> > I was wondering if anyone could shed some light on how to calibrate a
> > nocturnal for a given latitude. I understand the principal of
> > nocturnals, but have absolutely no idea of the angles involved either
> > for Polaris to Ursa Major or how latitude affects these. Any info
> > would be gratefully received. Thanks
>
> There is no latitude calibration - that is the beauty of these things.
>
> The calendar scales do need adjustment for the star (Kochab or the
> Pointers of Ursa Major) you set the hour handle to and the epoch
> (stellar precession).
>
> For instance, for Kochab lower culmination at mean local midnight (the
> hour handle then points downwards to the 'six o'clock' position) should
> occur on 4 November. For the Pointers, the mean local midnight lower
> culmination occurs on 7 September.
>
> -

A longitude adjustment, to convert from local apparent time to zone time,
is possible. I have made a nocturnal on which the first step is to set the
longitude by aligning the index arm with your location on a map engraved on
the main handle. The second step is to set the date by turning only the
date disk to align it with the index arm.
My map shows only the British Isles, but the same principle could be used
anywhere.

I have not seen any other nocturnals that show zone time in this way.
Perhaps because the notion of time zones is rather recent.

Chris Lusby Taylor
51.3N, 1.4W


-

Re: On Bezier Curves and analemmae

[Chris Lusby.Taylor]

John Carmichael wrote:

> I've never heard of a "Bezier Curve".  Is this the type of curve that Delta
> Cad draws when you use the "Spline" feature to connect points?
>
> John

Possibly. A Bezier curve is a specific flavor of cubic spline. They are very
quick to draw and easy to connect to one another to create a composite curve
with desirable properties such as continuity of curvature.

I don't know what Delta Cad offers, but typically you would specify the
positions of the ends of the curve and the positions of two other control
points. The curve goes from one end towards the first control point, then
gradually swerves towards the other and finally towards the end point. It does
not, in general, pass through the control points. By positioning the control
points, you can totally control the slope at the end points and you have some
control over where the curvature takes place along the curve.

With a single Bezier you can achieve a C or S shaped curve or a loop, like the
letter gamma, so with two you can make a figure 8. Whether you can reproduce an
analemma to within, say, one minute of time, I don't know but I bet you could.
You'd have to experiment with the best places to break the analemma into two
sections. The solstices might be good.

Beziers are great but there are things they cannot do. For instance, they
cannot accurately follow a circular arc.

Hope this helps


Chris Lusby Taylor
51.4N, 1.3W, 100%cloudy today


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Re: Equatorial Ceilng Dial

[Chris Lusby.Taylor]

If the mirror is sufficiently small, the reflected spot will appear to be a 
circle, but
it will actually be elliptic for low solar elevations. The hour and declination 
lines
will indeed be mirror images of those on a hemispherium.
BSS members who attended the meeting in Cirencester will recall Mark 
Lennox-Boyd's
description and model of a sundial very much like this, with a mirror and a 
curved
ceiling, that he was building in Italy. Does anyone know if it has been built 
yet?

Regards
Chris Lusby Taylor
51.4N 1.3W.

"fer j. de vries" wrote:

> Hi John,
>
> I have no idea if the reflected sunspot will be a circle or not.
> I should experiment with this to see what happens.
>
> In any case, assuming the mirror is in the center of the sphere, the
> reflected beam is perpendicular to the ceiling and it is rather easy to test
> this with a peace of cardboard.
>
> However, no sun to see this day.
>
> Fer.
>
> Fer J. de Vries
> ferdv+AEA-iae.nl
> http://www.iae.nl/users/ferdv/
> Eindhoven, Netherlands
> lat.  51:30 N  long.  5:30 E
>
> - Original Message -
> From: +ACI-John Carmichael+ACI- +ADw-johncarmichael+AEA-mindspring.com+AD4-
> To: +ACI-fer j. de vries+ACI- +ADw-ferdv+AEA-iae.nl+AD4-
> Cc: +ACI-Sundial List+ACI- +ADw-sundial+AEA-rrz.uni-koeln.de+AD4-
> Sent: Sunday, January 13, 2002 3:19 PM
> Subject: Equatorial Ceilng Dial
>
> +AD4- Hi Fer +ACY- others:
> +AD4-
> +AD4- Let's say you have a spherical room, built like a planetarium, where the
> +AD4- walls curve up into the ceiling and you locate your mirror in the 
> center.
> +AD4- (Actually, the room would be a quarter sphere, like an orange segment,
> with
> +AD4- one flat side being the floor, and the other flat side the southern wall
> +AD4- with the window with mirror).
> +AD4-
> +AD4- Would the sunspot be perfectly round all the time?  Also, what would the
> +AD4- hour and declination lines look like? (Like the lines on a 
> hemispherium?)
> +AD4- Would this be called an +ACI-Equatorial Ceiling Sundial+ACI-?
> +AD4-
> +AD4- John
> +AD4-
> +AD4- John L. Carmichael Jr.
> +AD4- Sundial Sculptures
> +AD4- 925 E. Foothills Dr.
> +AD4- Tucson Arizona 85718
> +AD4- USA
> +AD4-
> +AD4- Tel: 520-696-1709
> +AD4- Email: johncarmichael+AEA-mindspring.com
> +AD4- Website: +ADw-http://www.sundialsculptures.com+AD4-
> +AD4- - Original Message -
> +AD4- From: +ACI-fer j. de vries+ACI- +ADw-ferdv+AEA-iae.nl+AD4-
> +AD4- To: +ACI-sundial+ACI- +ADw-sundial+AEA-rrz.uni-koeln.de+AD4-
> +AD4- Sent: Friday, January 11, 2002 7:19 AM
> +AD4- Subject: Polar Ceing Dial
> +AD4-
> +AD4-
> +AD4- +AD4- Diallists,
> +AD4- +AD4-
> +AD4- +AD4- In my message of 2002-01-09 about the limits of a polar dial on a
> ceiling
> +AD4- I
> +AD4- +AD4- ended with:
> +AD4- +AD4-
> +AD4- +AD4- +ADw- Who has an inclined ceiling, higher at the south end?
> +AD4- +AD4- +ADw- Won't that be better?
> +AD4- +AD4-
> +AD4- +AD4- I wanted to know this for sure and I started with a ceiling with 
> an
> +AD4- +AD4- inclination of 160 degrees in stead of 180 degrees.
> +AD4- +AD4- A difference of 20 degrees as is shown in the attached picture.
> +AD4- +AD4-
> +AD4- +AD4- The mirror now gets an inclination of 0.5 ( phi - 20 ).
> +AD4- +AD4- For latitude 52 this is 16 degrees.
> +AD4- +AD4-
> +AD4- +AD4- The pattern on the now inclined ceiling also is a polar dial.
> +AD4- +AD4-
> +AD4- +AD4- I did not look for the extreme limits, but just gave it a chance.
> +AD4- +AD4-
> +AD4- +AD4- Following the same procedure the polar dial is cut off at about 
> 3.5
> hours
> +AD4- +AD4- before and after noon and it is seen that the mirror is less 
> inside.
> +AD4- +AD4- (distance CB ).
> +AD4- +AD4-
> +AD4- +AD4-  At the left the pattern for a south facing dial though CM with
> +AD4- (pin)gnomon
> +AD4- +AD4- CB is drawn.
> +AD4- +AD4-
> +AD4- +AD4- The mirror is at distance CM from C and that is shown with the 
> line KL.
> +AD4- +AD4-
> +AD4- +AD4- At summer solstice the mirror will be in the shadow of the edge 
> of the
> +AD4- +AD4- ceiling untill about 3.5 hours before noon and is shaded again 
> 3.5 hours
> +AD4- +AD4- after noon.
> +AD4- +AD4-
> +AD4- +AD4- So this configuration will work 7 hours at summer solstice.
> +AD4- +AD4- A great improvement compared with an horizontal ceiling.
> +AD4- +AD4-
> +AD4- +AD4- I only need to rebuild my house.
> +AD4- +AD4-
> +AD4- +AD4- Best wishes, Fer.
> +AD4- +AD4-
> +AD4- +AD4- Fer J. de Vries
> +AD4- +AD4- ferdv+AEA-iae.nl
> +AD4- +AD4- http://www.iae.nl/users/ferdv/
> +AD4- +AD4- Eindhoven, Netherlands
> +AD4- +AD4- lat.  51:30 N  long.  5:30 E
> +AD4- +AD4-
> +AD4- +AD4-
> +AD4- +AD4-
> +AD4- +AD4-
> +AD4- +AD4-
> +AD4- +AD4-
> +AD4-
> +AD4-

Re: international payments

[Chris Lusby.Taylor]

I used PayPal to pay for NASS CDs. They have some hidden charges for
international transactions that don't show up in any of their Web pages,
so please be aware that it will cost both parties a bit more than you'd
think. But international banking is always like that. Also be aware that
it takes up to a month to get an account becuase of the way they ensure
security.

Regards
Chris Lusby Taylor
Newbury, England
51.4N 1.3W

John Schilke wrote:

> Yes, one might also try the PayPal (.com) system.
> John
>
> > ... It should even be possible to
> > use your creditcard right from behind your PC.