Hi Dave, You are correct in your conclusions that analemmatic designs have hour points rather than hour lines and a universal analemmatic design would require a series of nested dials.
Fred Sawyer and Ron Anthony collaborated to produce a beautiful universal analemmatic design based on this concept. Look for the "NASS Madjet" in the latest NASS Compendium (7-2). The nested ellipses form a striking design which they interpret from Egyptian mythology as "Madjet, the papyrus sun boat on which Ra daily carries the great sun disk across the sky." Roger Bailey Walking Shadow Designs N 51 W 115 At 12:46 PM 8/9/00 -0700, Dave Bell wrote: > >I may be wrong, and it would be wise to verify this with Fer or someone >else far more knowledgeable about analemmatic dials, but I see a problem >with your vision of the dial: > >Analemmatic dials, as we have been discussing them, do not have hour >*lines*. They have hour *points* only, on the periphery of the ellipse. It >is the "responsibility" of the human gnomon to be tall enough to cast a >shadow all the way to the points. This sets the scale of the dial >somewhat, as a truly monumental dial would require Paul Bunyon (or at >least Wilt Chamberlain) as a gnomon! You can't beat it by - > >* Drawing hour lines, from the hour points to the gnomon foot, because the >foot moves with the time of year. > >* Drawing several "nested" dials at different scales (major axis length), >because the entire dial, including the date line/scale, is proportional to >the major axis. While you could draw lines connecting the corresponding >hour points, the central date lines would be of different lengths, so the >"gnomon" wouldn't have a unique point on which to stand. > >This also messes up your thought of painting footprints for different >height users, because all users, regardless of height, stand on the same >(date) point. Some just have to extend their arms over their heads, to get >a long enough shadow. > >To some extent, the dial design corrects for the "shortcomings" of the >users. Note that the date points for Summer are much closer to the North >rim of the dial, and the hour points for Noon are much closer to the date >line than 0600 and 1800. These automatically correct for the varying >shadow lengths per time of day and time of year... > >Does this make sense? > >Dave Bell >N37.29W121.97 > > > >
