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    Re: the Shovell Disaster
    From: Michael Daly
    Date: 2007 Nov 14, 14:40 -0500

    George Huxtable wrote:
    > And his octant didn't appear until over 20 years later, at its one-and only
    > public mention, noted in the Royal Society's Journal Book for 1699, when
    > Newton referred to it as having been used at sea by Halley.
    It was also published in the Phil.Trans. N. 465 in 1742, described as:
    "A true Copy of a Paper found, in the Hand Writing of Sir Isaac Newton,
    among the Papers of the late Dr. Halley, containing a Description of an
    Instrument for observing the Moon's Distance from the Fixt Stars as Sea."
    > For
    > example, Halley never even mentioned what instrument he used to obtain such
    > precise latitudes, in his three voyages, though it must have been something
    > special, to achieve the results he did.
    Latitude or longitude?
    Halley published his technique in an appendix to the second edition of
    "Mr. Street's Caroline Tables" around 1684.  He used the time of an
    observation of an occultation of a star by the moon (instead of lunar
    distances) and the instrument was simply a telescope.  What isn't clear
    is whether he used this technique on only one or on all three voyages.
    If he did use lunar distances, it is often suggested that he used
    Newton's, which E.G.R. Taylor says was constructed by Thomas Heath and
    may have been shown in his shop window.  However, I can't find much to
    support the claim that Halley used Newton's.  It is also possible he
    used one of his own design, the "folding-telescope on a radio latino
    with a screw adjustment" described in Cotter's "The Mariner's Sextant
    and the Royal Society".
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