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    Re: Lunars: Thomson's Tables
    From: Frank Reed CT
    Date: 2006 Apr 19, 08:22 EDT

    Hello Jan K.
    It is wonderful to see you  again. How long has it been... a year... two??
    You  wrote:
    "Nevertheless, Thomson's table was unique by its small steps and in  the
    consequence, by many thousands of calculations that were needed for  constructing
    it. One secret remains - how Thomson could find time for  calculating it
    throughout his life of a mainline mate and later the captain of  the brig?"
    As you know, many similar tables existed but Thomson's were  the most
    extensive. Thomson's were unique for including thousands of entries  which saved the
    sea-going navigator the effort of interpolation. But that means  only that the
    creator of the tables had to do the interpolation himself, or hire  someone
    to do it. He didn't necessarily have to do each calculation from scratch
    (though he could have if time permitted).
    And you wrote:
    "Thomson's  method was the FIRST Bowditch's method in his first editions.
    Only later  Bowditch moved his own (first) method from the appendix into the main
    text and  made it the chief lunar method in his compendium."
    That's not quite  right. I think if you check your own postings on this
    matter from a few years  back you'll find that you had it right back then.
    Thomson's method was the last  of the four added to the Navigator (it was listed as
    method #2 from 1837 to  1880). It appeared first in the edition of 1837 --the
    year before N. Bowditch  died. It's interesting to note that prior to this, in
    1826, Bowditch had  extended his own Table XX to include the effect of the
    "quadratic cross-term"  which is the only real extension in Thomson's tables. It's
    a minor thing, but it  does help in some cases. Unlike Thomson's, Bowditch's
    version was a brief table  with rather large steps so interpolation would
    often be required.
    And you  wrote:
    "I tried to download Zach's article on Thomson' table from the adress  that
    Frank hints at, but I got the paper from the year 1830, not 1829 I  asked"
    I can send you a copy. It's a brief note.
    I'll say again,  it's wonderful to see you posting here.
    42.0N 87.7W, or 41.4N  72.1W.

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