In a message dated 5/8/00 11:46:16 PM Eastern Daylight Time, [EMAIL PROTECTED] writes:
> Hi, I need help finding some equations for changing > between coordinate systems. Specifically, given the > hour angle of the sun (where 0 degrees is high noon), > my latitude, and the sun's declination, I wish to find > the sun's azimuth and elevation. Here are the Formulas: Let T=Hour Angle of sun, L=Latitude of location, D=Declination of sun, then: Azimuth=Atan(sin(T)/[sin(L)*cos(T)-cos(L)*tan(D)]) Altutide (elevation above horizon)=Asin(sin(D)*sin(L)+cos(D)*cos(L)*cos(T)) > Other questions: > > 1. Is elevation the same thing as altitude, i.e. the > angle between the sun and the horizon? Yes > 2. Is the calculation for azimuth the same one I've > been using for drawing hour lines on horizontal dials, > i.e. D = arctan( tan HA * sin LAT ) ? No. See above. > > 3. Have I used the term "hour angle" correctly? A > negative hour angle would mean it's morning, a > positive HA would mean afternoon, and HA=0 means the > sun lies in the observer's meridian. Yes. H=0 at solar noon. > Thanks in advance, > > Rod Heil Good Luck Bill Gottesman Burlington, VT 44.4674 N, 73.2027 W
