Sundials are interesting indeed, but some study is necessary.
On the WEB many sites will help you.
The ring dial you noted is in fact an equatorial sundial.
In use its inner ring lies in the equatorial plane.
The inner diameter of that ring is R.
The point on the date scale is from the centre: y = R tan decl.
Decl is the declination of the sun, relative to the date.
It is the angle the sun is north or south the equator.
That's all.
Best wishes, Fer.
Fer J. de Vries
Fer J. de Vries
De Zonnewijzerkring
mailto:[EMAIL PROTECTED]
http://www.de-zonnewijzerkring.nl
Home
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http://www.iae.nl/users/ferdv/index-fer.htm
Eindhoven, Netherlands
lat. 51:30 N long. 5:30 E
----- Original Message -----
From: "wee-meng lee" <[EMAIL PROTECTED]>
To: "Sundial" <[email protected]>
Sent: Tuesday, May 24, 2005 7:34 AM
Subject: How to calculate "gnomon" of ring sundial?
Hello,
I've always been fascinated by Sun dials and have just found this group
surfing around after making my first working Sundial using Shadowspro.
It's
found here: http://leewm.freeshell.org/origami.
All the sundials that I've made before didn't work in my location as I
didn't understand the concepts and they were designed for the more
northern
regions.
In the ring sundial found in http://www.pocketsundial.com/, how does one
calculate the the location of the hole in the centre portion that acts as
the gnomon? I'm sure the radius of the circle has something to do with
it.
I'm sorry if I used the wrong terms as I'm just picking up the vocabulary.
Thx very much :)
weemeng
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