I didn't do any structural research on the relation of the refelcted spot and the mirror size but I guess the the larger the mirror the larger the reflected spot.. Just imagine a mirror of 1m squaire: it will give an enormous spot. But use the mirror that most of you have on your left wrist: the glass of your watch: easy to experiment with it and you will see that it will carry long distances, hence small mirror will give a nice small spot that can be read more acurately.
Thibaud Chabot
At 07:40 24-1-2002 -0700, John Carmichael wrote:
Hi All: One last question about reflected sundials that I've been wondering about.. What is the mathematical formula that gives the diameter of the reflected sunspot if you know the diameter of the mirror and the projection distance? Let's say you're designing a ceiling sundial and are trying to decide how big to make your mirror. (Bigger rooms require bigger mirrors I would think. If the mirror is too small and the projection distance is very large, the sunspot would disappear I should think; and if the mirror is too large and the room is small, then the sunspot would be very big and precision would be sacrificed). As we have discussed, the projection distance and the size of the mirror are the principal factors that determine sunspot size, but I have a strong feeling that the size of the sunspot is also determined by the apparent diameter of the sun. Any thoughts on this and what the formula might be? 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>
--------------------------------------------------------------------- Thibaud Taudin-Chabot 52° 18' 19.85" North, 04° 51' 09.45" East, alt. -3.45 m home email: [EMAIL PROTECTED]
