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    Octant precision, was: Sextant precision
    From: Alexandre Eremenko
    Date: 2004 Sep 30, 23:42 -0500

    I think the following passage is interesting
    from the point of view of our recent discussions
    of star-to-star distances, sextant ultimate
    precision and the quality of old instruments:
    
    "On 8:30 November 14 we were on the meridian
    of the Flores island, and at noon within 12 leagues
    to the West in the direction W by S (101 1/4 deg)
    from Montevideo;
    from here I took my departure point as
    Lat. 34d54' S, and Long. 58d57'30" West of Paris...
    
    "I also used my stay on the shore to find the correction
    of my octant from the distances between the known stars;
    it turned out that the altitudes measured by this instrument
    were 2" less than the real ones,
    and I always used this correction since then."
    
    NO, I made no misprint: he is talking about 2 SECONDS!
    
    This is from the XVIII century book:
    Louis Antoine de Bougainville,
    Voyage autour du Monde
    par la fregate du Roi la Boudeuse
    et la flute l'Etoile,
    Paris, 1771.
    
    Any comments?
    In XVIII century, he could determine the correction of his
    octant as 2" from star-star distances??
    He was able to READ his octant to 2" ?
    
    Bougainville was the first French circumnavigator
    (1766-1769), and his book describing this voyage
    is aimed at explorers and navigators,
    rather the general audience.
    
    He also talks a lot about lunar distances. He departed
    2 years earlier than Cook, so the method was quite new then:-)
    Unfortunately I do not have the original book,
    what I am reading now is a Russian translation from
    the French original. That's why I do not cite what he says
    about lunar distances, to avoid double translation.
    Alex.
    
    
    

       
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