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    Lunars in 1766
    From: Alexandre Eremenko
    Date: 2004 Oct 1, 01:49 -0500

      Here is my translation from the Russian translation
    of a page from the book of Bougainville, (Paris, 1671)..
    He is talking about a fix
    by Lunar distances with the error of about 3.5'.
    (Which implies at most
    10" error in the measurement of the distance itself).
    This is with a Hadley octant made of wood:-)
    Can someone verify the precision of his fix with a modern map
    and comment this text?
    (Don't forget he is using Paris meridan as zero!)
    The cape of Vierges
    is called Cabo de las Virgenes now.
    It is near the entrance to the Magellan strait.
    I cite:
    
    "This fix, combined with bearings gives the following
    coordinates for the cape of Vierges:
    Lat. S 52d23' and Long. 71d25'20" West of Paris.
    Because the cape of Vierges is an interesting point
    for geography, I have to explain what made me believe
    that its position was fixed by me with almost
    absolute precision.
    
    "On November 27, afternoon, Chevalier du Bouchage measured
    eight Lunar distances whose averaging gave the
    longitude of 65d0'30'' (West of Paris) at 1h43m26s of
    real time; M. Verron on his side measured 5 lunar distances,
    whose average gave our longitude at the same time as
    64d57'. The weather was good and favorable for observations.
    On 29-th at 3h57m35s of true time, M. Verron, by 5-fold
    measurement of Lunar distances found the longitude as 67d49'30"
    (West of Paris).
    
    "Now, having found the place of the ship in view of cape Vierge,
    and taking as a basis [for dead reckoning - A. E.]
    the longitude determined
    on November 27,
    by averaging the results of observations of
    Chevalier du Bouchage, and M. Verron, we will obtain that
    the cape of Vierge is placed on the longitude 71d29'42" W of Paris.
    Obserevations at the moment of determination by bearings
    of position of cape Vierge would give the result of 38'47" more
    to the West. However, I suppose that one has rather to take as a base
    the observations of Nov. 27, because they were made several times,
    by two observers who did not communicate with each other,
    while their results differ only by 3'30", and seem so plausible
    that it is hard to reject them.
    
    "These observations were made using an English octant.
    The method of determining longitude in sea
    by way of Lunar distances to the Sun
    or to Zodiac stars is known for many years.
    Mr. de la Caille and  d'Apres, used this method in the sea,
    also with the Hadley octant."
    
    Alex.
    
    
    

       
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