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    Re: Index corr. for back sights, was: Octant as dipmeter
    From: Alexandre Eremenko
    Date: 2004 Nov 21, 12:16 -0500

    George,
    I suspect that there are some
    substantial (mathematical) problems
    with back sights in general,
    not just the rigidity of an instrument.
    
    All papers on the subject I read yesterday
    are divided into two categories:
    
    a) papers of theorists (like Wollaston,
    who did not actually sail, and I probably did
    not experiment with a quadrant)
    and
    
    b) papers of people who actually tried the back
    sights.
    
    Wollaston proposed exactly what I proposed:
    measuring the dip, and the procedure of
    back sight index correction.
    
    However all who actually tried repeat that
    this does not work.
    
    As a result, they soon gave up the idea of
    taking back sights. I am trying to understand mathematical
    reasons of this. I just don't believe that the
    main obstacle could be in sextant/octant rigidity:
    they knew very well how to make good instruments.
    
    Alex.
    
    
    

       
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