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    Re: Instrumental error?
    From: Fred Hebard
    Date: 2005 Apr 24, 16:28 -0400

    Bill wrote, in response to something I wrote:
    
    >> If you can get the standard deviation of Ho-Hc under 0.5'
    >> of arc on dry land, that's good enough for use at sea, especially
    >> on small vessels.
    >
    > I would like to get to a level where I can touch discs consistently at
    > a
    > 0.3' level or better. Have tried a few experiments with touching the
    > Sun to
    > a power line of roofline, and it seems easier.
    
    One trick is to set the sextant with the objects slightly apart, as
    appropriate to rising or setting, and wait for them to converge.  The
    biggest challenge then is timing the convergence accurately.  This is
    also a recommended trick for shots on water using a real horizon.  (It
    doesn't work for meridian shots, such as the sun at noon, btw).
    
    Fred
    
    
    

       
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