NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
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
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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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