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Re: Day's lenght
From: Zorbec Legras
Date: 2002 Dec 31, 15:34 -0500
From: Zorbec Legras
Date: 2002 Dec 31, 15:34 -0500
> Pierre Boucher [mailto:pboucher@LAVOILE.COM] asked: > > Does anybody know of a formula that would compute for a given > > latitude and a given date the day's length ie. how many hours > > from sunrise to sunset? In my first answer to Pierre I gave a simplified formula to compute the duration of half a day, from geometrical rise/set to/from meridian transit. The full formula to compute the exact duration is: Cos asd =(sin H - (sin L sin d)) / cosL cos d asd = semi diurnal arc (from rise to noon transit, in fact the pole angle) H = altitude of the sun (- 0�53' flag time; -6� civil twilight; etc) L = Latitude d = declination (at noon) the duration of a day is twice the asd in � ' " , or 2 asd/ 15 in h mn sec. If the chosen H is 0�, the simplified formula is used whitch is : cos asd (- tan L tan d) Cpt Legras. -- __________________________________________________________ Sign-up for your own FREE Personalized E-mail at Mail.com http://www.mail.com/?sr=signup Meet Singles http://corp.mail.com/lavalife