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    Re: Plastic sextants. was: GPS shortcomings.
    From: Dave Weilacher
    Date: 2005 Jun 9, 16:49 -0400

    A retired US Navy Commander friend who was reponsible for navigation aboard 
    ship on one of his assignments is of the opinion that the horizon is always 
    suspect near shore.  The argument is that the differences in temperature 
    between land and sea screws up the horizon that you see.
    Could this account for the discrepancy between every ones expectations and his measured results?
    -----Original Message-----
    From: Carl Herzog 
    Sent: Jun 9, 2005 4:26 PM
    Subject: Re: Plastic sextants. was: GPS shortcomings.
    George Huxtable wrote:
    >I'm rather surprised that John Kabel experienced such large errors, when
    >using his Astra from a beach (about 50 % within 3 miles). Was this
    >shot-to-shot scatter? How repeatable was a series of repeated shots at
    >close intervals? It could be explained by days of anomalous dip, but a 50%
    >frequency seems absurdly high. Does John have an explanation?
    I'm curious too. Results like that do not reflect the inherent
    capability of the sextants. I've never had results that bad with either
    a plastic Davis or a metal Astra underway on any size vessel. I've never
    tried shooting anything from the shore, so I don't know what other
    factors may confound accuracy there, but it seems like something else is
    wrong in this case.
    Dave Weilacher
    .IBM AS400 RPG contract programmer
    .USCG Master lic. 100 ton
    .ASA Sailing Instructor Evaluator

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