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    Re: Explanation by Mr. Stark needed
    From: Bruce Stark
    Date: 2003 Jun 12, 13:11 EDT

    Doug,
    
    Please don't hold me to my statement:  ". . . the moon being east or west of
    you doesn't mean you are west or east of her." I was thinking DUE east and
    west. In other words, a body's position angle is hardly ever the reciprocal of
    the azimuth. This is easily demonstrated with a piece of string on a globe.
    
    The ideal situation for getting local time or longitude is when a body is due
    east or west. That's when it is perfectly in line with the motion you want to
    measure, the earth's rotation. But to get GMT from the moon you have to
    measure the moon's motion along her orbit. The earth's rotation has nothing to do
    with it.
    
    Years ago, I picked a time from the Almanac and set up a hypothetical
    situation where a boat was expecting to be entering the English Channel in a few
    days. Night was falling and weather making up, but the single-handed navigator got
    a good cut with two stars, and the altitude of the moon. His LOP lunar put
    the boat well out in the Atlantic. Reassured, he went below.
    
    Trouble was, he was just west of the Scilly Islands. Although the moon was
    within 5? of due west, and all three altitudes more accurate than could be
    expected, the observation was a disaster. The moon's orbital motion, as I recall,
    was out of line with her altitude by 79?.
    
    Bruce
    
    
    

       
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