Hello all: I've been having lengthy discussions with Fer, Sarah Edmonson and Steve Lelievre about azimuthal (Dali) sundials. I have one more observation/question that I'd like to make, but I thought I'd throw it out to the List to get other people's input as well.
We briefly mentioned that for the vertical gnomon's shadow to reach the outer concentric date ring at mid-day, it would have to be extremely tall, especially at lower latitudes. (Here in Tucson at 32.5 deg. N. , the sun is only 9 degrees away from zenith on the summer solstice). Bill Gottesman suggested using a string tied to the gnomon's foot to artificially extend the shadow's length to to outer ring during the mid-day hours. (A telescoping rod serving as the vertical gnomon, like a car antenna, might work also). Here's another idea, but will it work? Another way to solve the gnomon height problem might be to make the inner ring the June ring, when the sun is highest and the shadow the shortest. The next ring would be July followed by May, August, April, Sept, March, Oct, Feb, Nov, Jan, and December as the outer ring. This ring order would place those summer short shadow months closest to the gnomon and the winter long shadow months further out. This ring arrangement would increase the number of hours where the shadow crosses the date lines and make the dial more functional. However, arranging the date rings out of monthly sequence would make it impossible to connect the hour lines in a nice curve. Instead, for each date ring, wouldn't there just be a little time line segment, unconnected to to hour line in the adjacent date ring? I'm wondering if my idea would work, and if so, if I can get Fer's spin program to do it. any thoughts anyone? John Carmichael Tucson Arizona p.s. for those of you still struggling to understand Dali and azimuthal sundials, don't make the same mistake I did by confusing the terms "Azimuth sundial" and "Azimuthal sundials". They aretwo completely different kinds of sundials and are designed on Zonwvlak using two different programs!!!
