At 11:26 PM 12/28/96 +-100, you wrote: > >Dear Mac, > >It depends on what point of zero-reference for the hour angle HA is taken: > >1. Rohr, Mayall: > > Hour angle HA1 is measured from the north (zero) to the east (positive). > > Resulting formulae: cosHA1 = +tanL.tanD > >2. Otherwise > > Hour angle HA2 is measured from the south (zero) > > Resulting formulae: cosHA2 = -tanL.tanD > > >(Note: cos(a+180)=cos(a-180)=-cos(a), giving the same result) > > >Regards, > > > >Hans Sassenburg > > > Hans,
Please forgive this humble and ignorant diallist if I am wrong, but I get the impression you are talking about the sun's AZIMUTH when you refer to measuring from either the north or the south. I think of the sun's hour angle as being an arc on the celestial sphere measured east and west of the local meridian with the measurement being centered on the Earth's axis and the arc parallel to the celestial equator. Charles Gann **************************************** * Sundials and The Author * * http://www.geocities.com/athens/1012 * ****************************************
