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    Re: Sextant accuracy with short distance to horizon
    From: Michael Wescott
    Date: 2001 Jun 22, 12:56 PM

    > Later we did the noon shot and his results were about 68 miles off for a
    > bunch of shots.  These were taken in Guemes channel with a local horizon
    > less than a mile away.
    
    As others have pointed out, there is a calculation/table for Dip
    when the sight is taken against a point that's closer (below) the
    visible horizon. And the error will be toward, so you should've
    calculated a position further south than you really were.
    
    But an error of 68' is too much. That implies a shore line closer
    than a tenth of a mile; about 170 yards if He is 10'. If you were
    that close, it explains the error.
    
    I think a good guess at the bulk of the error was a mis-reading
    of the sextant by a degree. Personally, I find that one of the
    easier errors to make, especially when the drum reads in the 50's.
    
    Off by a degree and the error reduces to about 8' which is quite
    reasonable considering the record from earlier in the day and the
    Dip-short situation.
    --
            Mike Wescott
            Wescott_Mike{at}EMC.COM
    

       
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