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    Re: Star-star distances for arc error
    From: Frank Reed
    Date: 2009 Jul 4, 18:27 -0700

    Paul, you wrote:
    "Now I'm more skillful at positioning both bodies in the split image
    horizon glass and swinging the arc. That last is important, I've found.
    The pair of stars should appear to collide instead of passing each other
    as the sextant is rocked. Contrary to what I expected, attempting to
    keep the stars in contact makes it harder to judge coincidence."
    
    Same here. Do you find also that you get better accuracy when you do that same 
    rocking motion when shooting lunars? 
    
    And:
    "When viewing a single star to check index error, that last technique is
    all you have, since swinging the arc has no effect."
    
    As Greg (and Bill B.) has noted, leaving a little "side error" helps in that case.
    
    And you wrote:
    "With more practice I may be able to judge star coincidences as well as I can 
    judge anything else through a sextant."
    
    In my own experience, star-to-star angles remain somewhat less accurate than 
    good lunar distance observations, but they have the singular advantage of 
    convenience being available at any moment on any clear night --and with a 
    multitude of choices in angle at any time. 
    
    
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