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    Re: Latitude by Lunar Distance
    From: Peter Fogg
    Date: 2006 Oct 9, 09:51 +1000

    On 10/8/06, Frank wrote:
    
    > ...you are apparently
    > working only to the nearest 0.01 degrees. That's much too coarse. You
    > should re-do the calculations working to the nearest 0.0001 degrees.
    > Then differences of 0.1 minutes of arc are much more likely to be
    > correct.
    
    At Lat N38d, Lon W070d, on 11 Oct 2006 (All at sea)
    GMT         Body               Azimuth        Altitude
    6h 36m     Aldebaran        134.616d        62.060d
                    Moon(Centre)   110.677          67.341
    Distance between bodies   11.412d
    6h 39m     Pollux                79.036d        34.175d
                    Moon(Centre)    111.618          67.882
    Distance between bodies    38.476d
    
    At Lat N41d, Lon W074d, on 11 Oct 2006 (Approx New York)
    GMT         Body               Azimuth        Altitude
    6h 36m     Aldebaran        132.171d        57.758d
                    Moon(Centre)   111.847          63.315
    Distance between bodies    11.37d
    6h 39m     Pollux                78.781d        31.723d
                    Moon(Centre)    112.735         63.828
    Distance between bodies    38.454d
    
    The differences between these results and those sent
    previously are negligible.
    
    > Also, please note that the observed distances I quoted (and
    > yes, they ARE correct) were distances from the Moon's limb to the star,
    > not the Moon's center.
    
    It seems that the centre of the moon is the relevant point of
    reference, as James R. Van Zandt points out.
    
    > Ah, but Peter, the difference in parallax IS due to a change in
    > position. That's why this works. :-)
    
    The correction for parallax is positive and that for refraction is
    negative. There will be an infinite number of positions where the two
    corrections can cancel one another, ie; the distances will be the
    same.
    
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