Fernando Cabral wrote: > > Hello > snip.... > And now one more question from a inquiring neophyte: > > What is the formula to calculate sunrise and sunset times given > latitude, longitude and declination (or perhaps the date)? > > Thank you. > > - fernando > > -- > mailto:[EMAIL PROTECTED] http://www.pix.com.br > Fernando Cabral Padrao iX Sistemas Abertos > [EMAIL PROTECTED] [EMAIL PROTECTED] > Fone: +55 61 321-2433 Fax: +55 61 225-3082 > 19º 37' 57.0" S 45º 17' 13.6" W > 15º 45' 04.9" S 47º 49' 58.6" W
Fernando, input : phi : is latitude decl: is sun's declination output : T :is half day length in degrees. formula : cos T = - tan phi . tan decl Sun rises at - T degrees Sun sets at + T degrees The answer is in local suntime. Convert T into hours by deviding with 15. Correct for longitude and equation of time if you want standard time. Not taken into account the diameter of the sun and the refraction. In gnomonics this is usual. Fer.
