Re: Seasonal Sunrise Marker

[J Lynes]

Extending Roger Bailey's treatment, if you know the time and direction of
sunrise you can easily estimate the time and direction of sunset, or
vice-versa:

Time of sunset = 24 - (time of sunrise)
Azimuths of sunrise and sunset are equidistant from the North-South
meridian, remembering that sunrise is east and sunset west of the meridian.

If you know the direction of sunrise or sunset at a given solar declination
D degrees North, you can easily estimate the time and direction of sunset or
sunrise at declination D degrees South:

Time of sunrise at D degrees South = 24 - (time of sunset at D degrees
North)
Azimuths of sunrise at D degrees South and sunset at D degrees North are
equidistant from the East-West line, remembering that in the Northern
hemisphere the former is South and the latter North of the East-West line.
You can interchange "sunrise" and "sunset" in these expressions.

If you have a vertical declining sundial with declination lines and a
horizon line, you have all the data you need to use the above information.

John Lynes

Roger Bailey wrote -
The times of sunrise and sunset can be easily determined on a vertical
declining dial that has declination lines. The horizontal line from the base
of the gnomon is the horizon line. The intersection of the declination line
and the horizon line shows the time of sunrise or set. This is of limited
use on south facing dials as the scale of the gnomon and resulting
declination lines is usually to great to show much more than the winter
solstice.

Re: Equatorial Ceilng Dial

[fer j. de vries]

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
[EMAIL PROTECTED]
http://www.iae.nl/users/ferdv/
Eindhoven, Netherlands
lat.  51:30 N  long.  5:30 E

- Original Message -
From: "John Carmichael" <[EMAIL PROTECTED]>
To: "fer j. de vries" <[EMAIL PROTECTED]>
Cc: "Sundial List" 
Sent: Sunday, January 13, 2002 3:19 PM
Subject: Equatorial Ceilng Dial


> Hi Fer & others:
>
> Let's say you have a spherical room, built like a planetarium, where the
> walls curve up into the ceiling and you locate your mirror in the center.
> (Actually, the room would be a quarter sphere, like an orange segment,
with
> one flat side being the floor, and the other flat side the southern wall
> with the window with mirror).
>
> Would the sunspot be perfectly round all the time?  Also, what would the
> hour and declination lines look like? (Like the lines on a hemispherium?)
> Would this be called an "Equatorial Ceiling Sundial"?
>
> John
>
> John L. Carmichael Jr.
> Sundial Sculptures
> 925 E. Foothills Dr.
> Tucson Arizona 85718
> USA
>
> Tel: 520-696-1709
> Email: [EMAIL PROTECTED]
> Website: 
> - Original Message -
> From: "fer j. de vries" <[EMAIL PROTECTED]>
> To: "sundial" 
> Sent: Friday, January 11, 2002 7:19 AM
> Subject: Polar Ceing Dial
>
>
> > Diallists,
> >
> > In my message of 2002-01-09 about the limits of a polar dial on a
ceiling
> I
> > ended with:
> >
> > < Who has an inclined ceiling, higher at the south end?
> > < Won't that be better?
> >
> > I wanted to know this for sure and I started with a ceiling with an
> > inclination of 160 degrees in stead of 180 degrees.
> > A difference of 20 degrees as is shown in the attached picture.
> >
> > The mirror now gets an inclination of 0.5 ( phi - 20 ).
> > For latitude 52 this is 16 degrees.
> >
> > The pattern on the now inclined ceiling also is a polar dial.
> >
> > I did not look for the extreme limits, but just gave it a chance.
> >
> > Following the same procedure the polar dial is cut off at about 3.5
hours
> > before and after noon and it is seen that the mirror is less inside.
> > (distance CB ).
> >
> >  At the left the pattern for a south facing dial though CM with
> (pin)gnomon
> > CB is drawn.
> >
> > The mirror is at distance CM from C and that is shown with the line KL.
> >
> > At summer solstice the mirror will be in the shadow of the edge of the
> > ceiling untill about 3.5 hours before noon and is shaded again 3.5 hours
> > after noon.
> >
> > So this configuration will work 7 hours at summer solstice.
> > A great improvement compared with an horizontal ceiling.
> >
> > I only need to rebuild my house.
> >
> > Best wishes, Fer.
> >
> > Fer J. de Vries
> > [EMAIL PROTECTED]
> > http://www.iae.nl/users/ferdv/
> > Eindhoven, Netherlands
> > lat.  51:30 N  long.  5:30 E
> >
> >
> >
> >
> >
> >
>
>

Re: Seasonal Sunrise Marker

[Sonderegger Helmut]

Hi to all,
I just saw the headlines of the attached tables in my last mail are not
correct. The attached tables show the azimuth of sunrise measured (N - E -
S - W), not sunset. The results don't change.
Sorry!
Helmut


Helmut Sonderegger, A-6800 Feldkirch, 47,25 N / 9,59 E
Email:  [EMAIL PROTECTED]
URL: http://webland.lion.cc/vorarlberg/28/sonne.htm
- Original Message -
From: "Roger Bailey" <[EMAIL PROTECTED]>
To: "Sonderegger Helmut" <[EMAIL PROTECTED]>
Sent: Monday, January 14, 2002 5:14 AM
Subject: RE: Seasonal Sunrise Marker


> Hi Helmut,
>
> You make a good point here. Let me look at it and get back to you.
Different
> ways of looking at it give different results. This is the value of this
> mailing list. It allows us to share ideas and develop better ones.
>
> Roger Bailey

RE: Equatorial Ceiling Dial

[Andrew James]

John, Fer, and others,

John asked : 
> Let's say you have a spherical room, built like a planetarium, where the
> walls curve up into the ceiling and you locate your mirror in 
> the center. ... Would the sunspot be perfectly round all the time?  

I think that the image of the sun coming from any part of the mirror (I'm
assuming it is a horizontal mirror for simplicity) is always circular, so
that if the mirror is very small compared with the room the sunspot will
approximate to a circle.  

However the circular image of the sun is blurred or enlarged by the apparent
size of the mirror (as seen from the sunspot, more or less) and this
enlargement will only be equal in all directions when the sun and its
reflection are both at the zenith.  From the sunspot, the mirror appears as
an ellipse and from the zenith it is the special circular case.  At sunrise
and sunset it appears almost as a line so the enlargement is almost purely
horizontal, and at intermediate altitudes the vertical enlargement of the
circle is less than the horizontal.  (The elliptical appearance of the
mirror varies slightly as you move up and down the image of the sun, hence I
write "almost".)

Regards
Andrew James

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-

Sundials on other planets

[Ross Sinclair Caldwell]

Combining an astronomy hobby with sundials, I wonder if anyone has thought 
of how a sundial on Mars or Venus might look (ignoring the thick venusian 
clouds for the experiment), or one on the Moon?


And what about designing dials for Earth that keep the different planetary 
times? So that one could set up a line of dials each keeping time on the 
different planets of the solar system.


This just popped into my head just now, so I haven't worked out any of the 
details, but I look forward to the response of anyone else who's willing to 
spend some time thinking about it.


Ross Caldwell
43.3166N
-3.4667E


_
Discutez en ligne avec vos amis, essayez MSN Messenger : 
http://messenger.msn.fr/

RE: Sundials on other planets

[Ian Clarke]

The sundial at the link below was originally designed to go on the Mars 
Surveyor mission that would have landed this year.  The dial would have doubled 
as a camera calibration object.  The mission was canceled in the revamp of 
NASA's Mars program, and I don't know if the dial will accompany a future 
lander or not.
 
http://antwrp.gsfc.nasa.gov/apod/ap990428.html
 
Ian Clarke
Hatter Planetarium
Gettysburg College, PA
 

FWD: RE: Sundials on other planets

[Ania Marczyk]

One of the things that they sent to Mars recently was a sundial. Picture at:

http://antwrp.gsfc.nasa.gov/apod/ap990428.html

>= Original Message From "Ross Sinclair Caldwell" <[EMAIL PROTECTED]>
=
>De-lurking after a big move (from California to Agde, France).
>
>Combining an astronomy hobby with sundials, I wonder if anyone has thought
>of how a sundial on Mars or Venus might look (ignoring the thick venusian
>clouds for the experiment), or one on the Moon?
>
>And what about designing dials for Earth that keep the different planetary
>times? So that one could set up a line of dials each keeping time on the
>different planets of the solar system.
>
>This just popped into my head just now, so I haven't worked out any of the
>details, but I look forward to the response of anyone else who's willing to
>spend some time thinking about it.
>
>Ross Caldwell
>43.3166N
>-3.4667E
>
>
>_
>Discutez en ligne avec vos amis, essayez MSN Messenger :
>http://messenger.msn.fr/


Totalise - the Users ISP
--
To become a member and a shareholder
visit http://www.totalise.net

Re: On conical gnomon sundials and anti-vandalic designs

[F.W.Maes]

Dear Anselmo and all,

> You can see one of these conical gnomon sundials in the web page of the
> city of Gent in Belgium. This is a clever and elegant design, and very
> easy to put into practice.

I assume you mean the sundial park in Genk (some 130 km east 
of Gent). The Genk site can be found at:
http://www.biol.rug.nl/maes/genk/welcome-e.htm
and the conical dial of Javier Bores is nr. 9. 
(Sorry, still no English text ;-)

> Another of its virtues is that these dials are more robust, ie.,
> VANDALS-PROOF, than ordinary ones. This is a property which, at least here
> in Spain, is an essential one (!). 

The weak point here are the steel cables used to keep the edge of 
the cone in a conical shape. These have to be repaired quite often, 
I believe.

> I know there are more dials with that
> kind of 'robusness' (for instance, several polyhedrons laid so that one
> casts its shadow over the other), but does anybody know about some more
> dials like these?

For instance its neighbor, #10.

Regards, Frans


Dr. Frans W. Maes
Dept. of Animal Physiology
University of Groningen
P.O. Box 14Tel.  : +31-50-3632357
9750 AA Haren  Fax   : +31-50-3635205
The NetherlandsE-mail: [EMAIL PROTECTED]

Re: Seasonal Sunrise Marker

[J Lynes]

Two words were carelessly omitted from the third paragraph of my last
posting.  Please accept my apologies.  It's hard enough to digest even when
the wording is correct!  Below is a corrected version of the posting:-


Extending Roger Bailey's treatment, if you know the time and direction of
sunrise you can easily estimate the time and direction of sunset, or
vice-versa:

Time of sunset = 24 - (time of sunrise)
Azimuths of sunrise and sunset are equidistant from the North-South
meridian, remembering that sunrise is east and sunset west of the meridian.

If you know the time and direction of sunrise or sunset at a given solar
declination
D degrees North, you can easily estimate the time and direction of sunset or
sunrise at declination D degrees South:

Time of sunrise at D degrees South = 24 - (time of sunset at D degrees
North)
Azimuths of sunrise at D degrees South and sunset at D degrees North are
equidistant from the East-West line, remembering that in the Northern
hemisphere the former is South and the latter North of the East-West line.
You can interchange "sunrise" and "sunset" in these expressions.

If you have a vertical declining sundial with declination lines and a
horizon line, you have all the data you need to use the above information.

John Lynes

Roger Bailey wrote -
The times of sunrise and sunset can be easily determined on a vertical
declining dial that has declination lines. The horizontal line from the base
of the gnomon is the horizon line. The intersection of the declination line
and the horizon line shows the time of sunrise or set. This is of limited
use on south facing dials as the scale of the gnomon and resulting
declination lines is usually to great to show much more than the winter
solstice.

Re: Acadian domestic sundials

[Edley McKnight]

Hi Fer,

Ahh!  That explains the single knife cut sundial then!!  Thanks!
So you hold the blade down, edge to the left and flat like the 
horizontal plane with your thumb up and along the polar axis then 
draw it toward you while rotating around your thumb as a fixed axis.  
Yep, that winds up being vertical at the 72 degrees west of south, 
just like it should be. ( here at 43.126 degrees North Latitude ) ( 
well, if you are right handed anyway. )

I never could understand the thumb tilt thing til I received this 
explanation.

Original text ---
> A simple way to show what a Babylonian hour is, is to rotate your
> horizontal plane ( for Bab. time 0 hours )  around a pole style and after
> each 15 degrees you have the plane for the next Babylonian hour. In
> reverse this may be used to see the Italian hours and the horizontal plane
> counts for It. 24.
> 
> The intersection of each plane with no matter what surface gives the
> appropriate B. or I. line on that surface.
> It is very nice to make a simple model to see how such a plane acts in
> space.
> 
> BTW, the same principle may be done with a plane 66.5  degrees angled to a
> polestyle and you may see how the ecliptic circle moves in space relative
> to your horizon. Divide the ecliptic in 12 parts and you may see how each
> sign rises and sets. Such simple experiments are sometimes eye openers.
> 
> Fer.
> 
> Fer J. de Vries
> [EMAIL PROTECTED]
> http://www.iae.nl/users/ferdv/
> Eindhoven, Netherlands
> lat.  51:30 N  long.  5:30 E
> 
> - Original Message -
> From: "Warren Thom" <[EMAIL PROTECTED]>
> To: "Steve Lelievre" <[EMAIL PROTECTED]>;
> 
> Sent: Saturday, January 12, 2002 2:17 PM
> Subject: Re: Acadian domestic sundials
> 
> 
> > Hi Steve,
> >
> > The answer is yes,  to the question "can shadow plane dial be
> > constructed
> to
> > show hours to sunset (Italian hours)?"   You can think of the plane for
> one
> > hour before sunset as the horizontal surface  15° to your west (oops -
> > or
> is
> > that east??) on the earth and at your latitude.  A terrella would show
> this
> > plane nicely.  Two hours is the horizontal surface 30° away.
> >
> > Maybe Mac Oglesby has caused me to think more in "planes" but the last
> issue
> > (December 2001) of the Compendium had some good articles on lines,
> > planes and surfaces.  Steve Luecking had some very nice graphics showing
> "planes".
> > Gianni Ferrani describes the kalieidoscope cube that allows light only
> > in certain planes to pass through.  Mac showed some student (hour plane)
> dials.
> > Fer had  an article on polar bifilar.  It helped me understand Fer when
> > Claude Hartman reported on the math work of Rafael Soler Gaya.  I am
> > still digesting page 5 on how to calculate the lines and planes.
> >
> > Warren Thom ( 88W  42N)
> >
> > > Edley mentioned hearsay of a window dial, thus:
> > >
> > > "[The source] said they carved out deep narrow notches which, when the
> sun
> > > fully filled the notch, it was that particular time".
> > >
> > > That's sounds very much like a shadow-plane dial, but reversed to use
> > > illumination rather than shadow as the indicator. But according to the
> > > report, these dials were used to indicate time left before supper.
> > > This situation got me thinking - could a shadow plane dial be
> > > constructed in
> > such
> > > a way as to show time since sunrise / time to sunset? The descriptions
> > I've
> > > read, as I remember them, all relate to modern hour markings.
> > >
> > > Steve
> > >
> > >
> >
> 
> 
-Original text