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    Re: Longitude by Sunrise example
    From: Joe Schultz
    Date: 2010 Feb 4, 15:38 -0800

    Jeremy,

    Go to: http://aa.usno.navy.mil/data/docs/RS_OneDay.php

    then scroll down to Form B. Enter:
    2009 July 1
    Longitude east 0 degrees
    Latitude north 10 degrees
    Time Zone 0 hours east of Greenwich

    Hit <Get data> button and you should get sunset at 1825 UT.
    Then hit <Back to form> button and repeat for latitude N20.

    Ought to be equivalent to the paper almanac, and you're off to the races.


    Almanac
    -------
    Sunset N20 1844
    Sunset N10 1825

    Lat Corrn = (17-10)/(20-10)*(1844-1825) = 13.30min = 13min

    LMT = 1825 + 13min = 1838

    Lon Corrn (ZT) = (135 - 129) * 4d/min = 24min

    Sunset (ZT) = 1838 + 24min = 1902


    Hope this helps. Perhaps you can "cheat" your program, too. I have a graphical Lat Corrn calculator if you're interested in "beating" that confounded double interpolation table.

    Joe

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