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    Re: Octant precision
    From: Alexandre Eremenko
    Date: 2004 Oct 1, 12:05 -0500

    Dear George,
    I was pleased to learn from your citation
    of Bougainville's log that M. Verron apparently used
    the same star-to-star distance to check his
    octant in 1766 as I did 2 days ago,
    and for the same reason: they were visible almost
    on the same vertical (!?), both from my balcony (Sept 29, GMT 0:0)
    and from Montevideo, sometime in November 1766:-)
    (My report on this observatiopn was posted to the list on
    Sept 29 22:57:46 EDT under Re: star-to-star).
    But some little points still remains confusing:
    The translation you cite says:
    >taking apparent distances of the Eagle
    >and the Lyre Wega [an editor's
    >footnote here states that these terms were in
    >common use at the time to
    >describe the constellation Aquila (Arcturus) and Lyra (Vega)]
    >along the
    >same vertical,
    The editor's footnote seems to be incorrect:
    Arcturus is in the constellation of Bootes (not Aquila!)
    It is Alpha Bootes. And Alpha Aquilae is Altair.
    Now, what does it mean "common use...on the same vertical"?
    This depends on the time and position! Sometimes on the same,
    sometimes not.
    I am also pleased to know that the
    apparent precision of my observation
    would be sufficient to detect a sextant error of 2'.
    (The actual correction of my sextant seems to be much smaller).
    So probably they did not do better in 1766 with a Hadley octant
    than I do in 2004 with a SNO-T sextant:-)
    This is a great consolation for me; the statement about 2",
    which turned out to be a misprint was disturbing:-)

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