The easy, elegant formulae that you can use to determine sun rise and set phenomena are:
Sunrise time t: Cos t = Tan L x Tan D Sunrise location: Cos Z = Sin D / Cos L Sunrise Path: Cos psi = Sin l / Cos D where L is the Latitude, D is the Declination, Z is the azimuth, psi is the angle of the sun's path with the horizon, and t is the time, as an angle, from noon when the sun is at the zenith and t = 0. Be aware of the ambiguities in solving these trig functions by referencing them to the conditions at the equinox when the declination is zero. Then the time angle is +/-90 degrees or +/-6 hours and the azimuth is 90 or 270 degrees, due east or west. These relationships are based on the special case when altitude of the center of the sun is zero. Corrections for the observed position considering semi-diameter (16 minutes), refraction (~34 minutes) and dip due to the height of the observer are not considered. The equation for this case are ab bit more complicated but still solvable on a pocket calculator. Time is the local apparent time and must be corrected for longitude and the equation of time, to give civil or clock time. I hope this is what you were looking for. Roger bailey N 51 W 115 At 09:20 AM 9/6/99 MDT, [EMAIL PROTECTED] wrote: >Hello all > >I am an outsider to this list, and I wonder if this question is in topic, >but: >I would like to know if anyone could give me the formula or algorithm to >calculate the time of sunrise/sunset/noon given the date and the locale >coordinates. >I already have a program to do that, but I am looking for a formula that I can >use, for example, in a worksheet. >Any help would be appreciated. > >---Joao Azinhais >Lisbon >PS: I would be very grateful if the reply could be also sent to me directly >([EMAIL PROTECTED]) as well as to the mailing-list, since I am not >registered in it. Thank you. > > >____________________________________________________________________ >Get free email and a permanent address at http://www.netaddress.com/?N=1 > >
