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    Re: Latitude and Longitude by "Noon Sun"
    From: Jim Thompson
    Date: 2005 Jun 6, 06:39 -0300

    > -----Original Message-----
    > From: Robert Eno
    > An old friend of mine, who passed away a few years ago, and who was an
    > experienced navigator for over 60 years, once told me that the
    > noon sun shot
    > was overrated; that all you had to do was to take a few shots with an
    > interval of 2 - 3 hours then transfer one of the LOPs. Fred and a
    > number of
    > other list members seem to agree, and so too, do I.
    In Sumner's little pamphlet from the 1800's he showed how to do a celestial
    fix from two morning sun sights.  On Page 11 (reproduced in Peter Ifland's
    book):  "And likewise if two altitudes be observed, the times being noted by
    Chronometer, and the two lines, corresponding to the two altitudes, be
    projected as before, then both the true Latitude and the true Longitude is
    found at the intersection of the two projected lines."
    That, I think, was the recorded point of discovery of the celestial fix in
    human history.  His ship was becalmed, so that he had only moved about a
    mile between the two sights, while the sun had travelled further during the
    intervening hours, yielding crossing LOP's.
    (Michel Vanvaerenbergh and Peter Ifland. Line of Position Navigation: Sumner
    and Saint-Hilaire: the two pillars of modern Celestial Navigation. Unlimited
    Publishing LLC. Includes a reprint of the entire 1843 first edition of
    Sumner's book, and translations of two key articles by St Hilaire.)
    Jim Thompson
    jim3 at jimthompson dot net
    Outgoing email scanned by Norton Antivirus

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