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    Re: Point Venus, May 1774
    From: George Huxtable
    Date: 2007 Apr 29, 18:09 +0100

    Alex wrote on 25 April  about Cook on Tahiti
    | My calculation outlined in the previous message implies
    | that the going of the Clock from May 2 to May 6 was
    | approx 22m33sec per day.
    I think Alex has corrected those numbers in a later message.
    | What sort of "astronomical clock" was this, I don't know.
    | And why did not they use chronometers instead.
    Cook didn't have a chronometer, on this, his first voyage. Anyway, on land,
    a good pendulum clock, compensated for temperature (gridiron) and calibrated
    against sky objects, should be better than any early chronometer.
    | 2. Moon's altitude. Here something happens that I cannot
    | understand. The average error in Moon's altitude
    | was +6' on May 2 (average of 5)
    | and +7'8 on May 6.
    | The stated Index errors were +1' and +3', respectively.
    | Which leaves us with unaccounted 5'.
    | The only plausible explanation I have for this 5'
    | is that they had a substantial dip, which they did not record
    | in their account...
    When you are comparing Cook's altitude observations, what times are you
    using? Remember, he used apparent time, as did the Almanac then, whereas
    modern calculations expect GMT. Has that been taken into account?
    contact George Huxtable at george@huxtable.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
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