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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Day's lenght
From: UNK
Date: 2002 Dec 31, 14:08 -0500
From: UNK
Date: 2002 Dec 31, 14:08 -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? For a web page that performs the calculation (and whose source you can steal code from), see the NOAA page at http://www.srrb.noaa.gov/highlights/sunrise/sunrise.html . It has pointers to other Sun calculators and discussions of the formulae and corrections. Juergen Giesen has a nice explanation of the geometry of the problem at http://www.jgiesen.de/astro/solarday.htm . The page also points to other pages which contain Java applets to perform this and related calculation. However, this being a group emphasizing traditional methods, you should look at http://www.uwsp.edu/physastr/rislove/astrolabe/suncrss.htm, which shows how to solve the problem using an astrolabe. -- Peter
