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    Re: Friendly challenge : Jupiter Lunar Exercise 09 Feb 2011A
    From: Lars Bergman
    Date: 2011 Feb 16, 10:09 -0800

    Dear Antoine,
    Many thanks for you kind words, but I wouldn't call my method unique, rather more classic than the other soultions presented.

    Use the sun sight to determine local time, use the Jupiter-Moon distance to find Greenwich time, the difference between these times is longitude, provided that your latitude is known. If you don't know the latitude, assume one. With the Sun's azimuth you get a LOP on which the sun altitude will be constant. Then just cross this LOP with a standard Moon LOP.

    It may be possible that one iteration could be beneficial in this case; knowing GMT you could calculate Jupiter and Moon altitudes at your first fix, then "uncorrect" them to sextant altitudes, and use them for the lunar clearing. I did only a linear extrapolation of the altitudes and this is not perfectly correct, as Frank pointed out, as the rate of altitude change is not constant, also an error in the rate of change used will grow. Using calculated altitudes based on the first solution would probably give another watch error that could be used for a regular Sun-Moon fix. But why worry - you already knew your whereabouts!

    We have quite a lot of snow here, about 25' SSE of Arlanda, and moderate temperature, minus 5 Celsius.

    Lars


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