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    Re: Perpendicularity check
    From: Alexandre Eremenko
    Date: 2004 Sep 22, 19:14 -0500

    Dear Fred,
    Thanks for your prompt reply to some of my questions.
    
    1. Bowditch (the online version I have) says the same as
    the authors of other sextant books I read; this does not
    address my question. Same about Bruce Bauer (which I have).
    
    2.
    > Until you get an almanac,
    > tAhe US Naval Observatory has a very nice
    > site
    > at  from which you can obtain
    
    Great!! Thanks! If I knew this earlier, I would not
    spend money on a 2004 Almanach.
    (Next time I will be sailing will be definitely not earlier than next
    summer. And until then I can use this wonderful web site
    for my "balcony
    navigation").
    
    > The old inverting telescopes had one nice feature for
    > observing lunars,
    > which was a cross hair reticule.
    
    When I said that my Soviet inverting scope is of poor quality
    I did not specify the details (being afraid that my message
    is too long anyway, and may be non-interesting for most
    because of the abundance of detasils). One point about
    this scope is that you
    cannot focus simultaneously on the cross hair and a remote object.
    And this is a constructive defect, not of this particular scope.
    
    > My understanding is that observed lunar distances will be too
    > large if
    > the sextant is not properly oriented.
    
    I don't understand this argument. I don't understand
    how cross hair are going to help. It seems to me
    that the usual "rocking" procedure will do the job.
    But I have not tried the lunar distances yet.
    I tried star distances (as described in Bruce Bauer for
    testing a used sextant).
    The distance Arcturus-Dubhe seems to indicate that my sextant
    error is at most) 0.3'.
    
    Alex
    
    
    

       
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