thought I could ask.)
--Art
-Ursprungliche Nachricht-
Von: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Auftrag von Tim Yu
Gesendet: Tuesday, January 08, 2002 3:22 AM
An: Sundial List
Cc: Tim Yu
Betreff: RE: Polar ceiling sundial
[David]
What is a caustic curve?
See the website
: Was Re: Polar ceiling sundial
On Sun, 6 Jan 2002, fer j. de vries wrote:
The max. altitude of the sun h = 90 - phi + 23.5 degrees.
This reminded me of something I saw recently, that was a bit of a puzzle:
I live at 37.3N latitude. This puts the mean plane of the Ecliptic at
something like
To: J Lynes ; Anselmo Pérez Serrada ; Sundial,
Mailinglist
Sent: Sunday, January 06, 2002 7:01
PM
Subject: Re: Polar ceiling sundial
Hi John,
There are several limitations to concider but the
principle still is true.
The problems you mention occur at
latitudessmaller
The BSS sundial glossary has the following entry under Types of Dials:
reflecting ~: these dials have no gnomon, but reflect sunlight by means
of a semi-cylindrical mirror, set with the axis of the mirror parallel
to the polar axis. The mirror reflects the light to form a caustic curve
amongst
[David]
What is a caustic curve?
See the website:
http://www.cacr.caltech.edu/~roy/Caustic/
A simple Java applet demonstrates how a caustic curve is formed by
parallel light rays bouncing off a cylindrical, reflective surface.
Tim
Hello David,
See BSS Bulletin 98.1, page 30, _Reflecting Sundials_ by C.M. Lowne.
The article includes a section, The Cycloid as a Reflector, mentioning
that the cusps (of the reflected caustic) are neither evenly-spaced with
time nor did they lie on a straight line. However, the edge of
Thanks, Fer. Apologies all round, and especially to
Anselmo. I now think his proposal would work after all. But only in
the winter months. At noon at the equinox the reflected beam would be
vertically above the mirror. During the summer months the beam would be
reflected south of the
I thought I might share a simple drawing (URL below) that illustrates
Anselmo's idea. In the drawing the Sun is on the Equator so the angle
of the Solar rays onto the respective surfaces (polar dial plate and
ceiling) is 90deg. However, it can be seen that this relation holds
throughout
Pérez Serrada ; Sundial,
Mailinglist
Sent: Sunday, January 06, 2002 10:34
AM
Subject: Re: Polar ceiling sundial
Thanks, Fer. Apologies all round, and especially to
Anselmo. I now think his proposal would work after all. But only
in the winter months. At noon at the equinox
- Original Message -
From: Luke Coletti [EMAIL PROTECTED]
To: Anselmo Pérez Serrada [EMAIL PROTECTED]
Cc: Sundial, Mailinglist sundial@rrz.uni-koeln.de
Sent: Sunday, January 06, 2002 6:03 PM
Subject: Re: Polar ceiling sundial
I thought I might share a simple drawing (URL below
Subject: Re: Polar ceiling sundial
I thought I might share a simple drawing (URL below) that illustrates
Anselmo's idea. In the drawing the Sun is on the Equator so the angle
of the Solar rays onto the respective surfaces (polar dial plate and
ceiling) is 90deg. However, it can be seen
On Sun, 6 Jan 2002, fer j. de vries wrote:
The max. altitude of the sun h = 90 - phi + 23.5 degrees.
This reminded me of something I saw recently, that was a bit of a puzzle:
I live at 37.3N latitude. This puts the mean plane of the Ecliptic at
something like 52.7 degrees elevation. Near the
Hi, everyone!
Maybe some of you didn't notice that if you lean
the mirror towards the
South so that it's slope equals half of your
latitude then (a small
hand-made wedge would do the job quite well) you get a polar sundial
on the ceiling, with all its analemmas paralell to
the meridian
On Sat, 5 Jan 2002, [iso-8859-1] Anselmo P?rez Serrada wrote:
Maybe some of you didn't notice that if you lean the mirror towards the
South so that it's slope equals half of your latitude then (a small
hand-made wedge would do the job quite well) you get a polar sundial
on the ceiling, with
:30 N long. 5:30
E
- Original Message -
From:
J
Lynes
To: Anselmo Pérez Serrada ; Sundial,
Mailinglist
Sent: Saturday, January 05, 2002 8:59
PM
Subject: Re: Polar ceiling sundial
Anselmo Perez Serrada wrote -
"Maybe some of you didn't notice that i
the polar ceiling sundial separately... I'm sure that if you compare the
result with
the one obtained by a GPS compass you could hardly tell the difference.
Anselmo Perez Serrada
[ 41.63 N 4.73 W]
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