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    Re: Day's lenght
    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

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