The approximate formula that does not correct for semi-diameter and refraction is : Cos t = -Tan Lat x Tan Dec. This simple formula is easily solved with pocket calculators.
This formula is based on a reduction of the navigators' equation: Sin Altitude = Sin Lat x Sin Dec + Cos Lat x Cos Dec x Cos t, for Altitude = 0. For a more accurate result, solve the more complicated equation for an altitude of - 48' (~16' for semi diameter and ~32' for typical refraction). I will forward some previous postings on this topic. Roger Bailey, Walking Shadow Designs, N51:05 W 115:22 At 08:05 AM 10/1/98 -0400, Fernando Cabral wrote: >Hello > > >Concerning my previous question about "declination by calculation" I >received >several useful answers. They all lead to the same formula. Since >different >people took different approach a had a very good opportunity to learn >a lot. Some just gave me a formula (which was what I expected at first); > >some offered more background information (which was great). > >I think I have thanked everyone that helped me in a private message. >Here I >say "thank you" again for each one of you that helped me. > >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 > > >
