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    Re: Request for help re sunset predictions.
    From: George Huxtable
    Date: 2005 Apr 7, 00:45 +0100

    Henry Halboth wrote-
    
    >I have rather extensive examples of Longitude determination by sunset +
    >sunrise which alternately use both upper and lower limbs at the time of
    >occurrence. In any example that I have access to the resultant negative
    >altitude is used in a conventional Time Sight solution. These examples
    >are c. 1900 and make no reference to special tables and, to me at least,
    >there seems to be little need for any such as the solution is relatively
    >simple.
    
    ===================
    
    Thanks, Henry.
    
    Yes, I agree, there's no problem in calculating that hour-angle from
    spherical trig. I can do it, and so, no doubt, could Scoresby, if he had
    to.
    
    It's just that he says specifically that he got it from a table that makes
    me wonder what that table was.
    
    I agree, too, that it's perfectly possible to use upper or lower Sun limb,
    against the horizon, for a time-sight, or perhaps both alternately. I ask
    Henry which of these a professional mariner would refer to as "the moment
    of sunset".
    
    George.
    
    ================================================================
    contact George Huxtable by email at george---.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ================================================================
    
    
    

       
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