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    Longitude by lunar distance
    From: Paul Pauliukonis
    Date: 2012 May 10, 10:42 -0700

    How does one obtain longitude by lunar distance.

    I always thought that lunar distance measurement gives accurate GMT and then one uses the GMT to calculate longitude by using sun/moon line-of-position (LOP).

    In Joshua Slocum's book Sailing Alone Around The World, he states that the longitude is the difference between GMT (obtained by lunar distance) and Local Mean Time - LMT ("finding it is a simpler matter" p.104).

    My confusion rises from the fact that the LMT has to be accurate, since an error of four minutes equals one degree. Slocum's alarm clock did not even have a minute hand, so how did he accurately calculate LMT? He claims longitude accuracy of a few miles.

    Any comments on this subject will be very appreciated - paul

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