Hi Wee-Meng Congratulations on making your first sundial. you are lucky in Singapore in being so close to the equator. Instead of a truly horizontal dial, you could use any polar sundial, inclined by just one degree from the horizontal. I was in Singapore last year and admired the sundials in the Botanical Gardens. But I noticed that the armillary sphere dial in the orchid garden was set exactly horizontal, not at one degree. This is a mistake.
You ask about the hole in the gnomon of a universal ring dial. Its position is dictated by the sun's declination (north or south of the equator). This is known for any date, so the scale is of dates. Having set the hole to the correct declination for today, you can suspend the dial and let it rotate until the spot of light falls on the dial. This then not only tells the time but also shows you the direction of north-south. But you have to know if it is before or after noon, as you could select the wrong one (It doesn't allow you to distinguish between 10am and 2pm, for example). Best wishes Chris Lusby Taylor 51.4N 1.3W ----- Original Message ----- From: "wee-meng lee" <[EMAIL PROTECTED]> To: "Sundial" <[email protected]> Sent: Tuesday, May 24, 2005 6:34 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 > > > - > -
