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    Response to "Old Nav. Tech..."
    From: Maurice Millard
    Date: 1998 Jul 23, 7:45 AM

    Well, first let me say my post certainly awoke the list.
    
    Last night, I took a quick look at Bowditch, a 1977 edition.  In the section
    on Lunar Distance's, it made the statement (I am not quoting) the gist of
    which was that almanacs were available with this data prior to 1500, and
    Amerigo Vespucci was thought to have used this technique on his voyages.
    
    So possibly the data was available.
    
    Rick Emerson Comment: The apparent solar motion could be derived analytically
    using the Newtonian Theory of Gravitation, because it could be treated as a
    "Two Body Problem."  The Lunar motion would have to be treated as a three body
    problem.  This per my recollection was never solved analytically.
    
    The Almanac data for Lunar information was as I understand developed
    empirically.  That was Maskelyn's (Sp?) life's work.
    
    Peter' Smith's Cooment: ".... doubt that accurate tables of Lunar Distance
    existed in Columbus's time.."  I tend to agree, but it depends upon your
    definition of accuracy.  Potentially if they were fairly short term tables
    they might not be too bad.  Also, what alternative was available?  Whatever
    level of accuracy they yielded, it was probably better than anything else
    available at that time.
    
    Dan Hogan had several comments: First on Columbus's mathematical competence.
    He didnt have to necessarily do the calculations himself.  For, example, on
    James Cook's voyages of discovery, Lunars were used.  The crew compliment
    contained a "tame" astronomer, presumably to do the gruntwork.
    
    Second point: Dan makes the comment on an "hour glass."  You do not need to
    know the time using the Lunar method.  That's why the use of the method
    persisted so long, well into this century in fact.
    
    Good responses, I found several of them insightful and informative.
    
    Maurice Millard
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