In the October 2000 BSS Bulletin, there is an interesting article by Allan Mills called "Backwards Motion of The Shadow of a Sundial".
While I don't understand all the math Mr. Mills presented, the article shows that at lower tropical latitudes on or near the summer solstice, the sun can have two different hour angles at the same azimuth! This seemed impossible at first, but the diagram in figure 5 makes this clear. Maybe this article will help best John Carmichael >Steve L, > >I think there can be 2 hour angle solutions for a single azimuth. I think >one h.a. will be less than 90 degrees, and the other greater than 90. See >attached DeltaCad file. I wish I could comment on the derivation of your >math, but I am unfamiliar with your arctan, arc cos solution for ha. I hate >to say it, but this is where spherical trig will yeild the answers. Any >takers? > >Bill G. > >Attachment Converted: C:\STARNET\EUDORA\STEVEAZI.DC >
