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Subject: Lunar Distances
From: Greg Gilbert (GilbertG@XXX.XXX)
Date: Mon Feb 04 2002 - 22:31:13 EST
I've been trying to work through the example given by George Huxtable in
"About Lunars". It's a great way to try to understand the subject, and get
a feel of the calculations done by early navigators.
I've had a problem however, in that I think there is a typo in one
calculation.
I've followed the calculation for Predicted Lunar Distances - OK.
I've followed the calculations for observed and corrected Sun and Moon
altitudes - OK.
However, correcting the Observed Lunar Distance (105 degrees 50.5 minutes)
by adding the semi-diameters of Sun and Moon (16 minutes for the Sun and
16.4 minutes for the Moon) gives me an answer of d = 106 degrees 22.9
minutes, not 107 degrees 22.9 minutes.
Putting this into the formula for clearing the Lunar Distance gives me an
answer for D of 105 degrees 50.2 minutes.
I don't think this is correct because this gives me a GMT time for the
observations of 15:53:04, which doesn't tally with the estimated time of
"something between 1700 and 1800 GMT", and the watch time of 17:36:43.
Could the watch be incorrect by 1 hour, 43 minutes and 39 seconds?
Can someone help me here?
Greg Gilbert,
35o10' S, 138o42' E.
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