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    Re: lat/long from meridian passage
    From: George Huxtable
    Date: 2011 Jan 26, 10:08 -0000

    Gary wrote-
    "A simple way to deal with the changing declination for determining LAN is
    to adjust your course to account for the movement of the sun."
    
    But (as he adds later) that is useful only for courses that are due East or
    West. In which case, isn't he adding an extra layer of complication that
    navigators would really be better-off forgetting about?
    
    He continued-
    
     "The sun changes declination fastest around the equinoxes and then it is
    only at the rate of one knot north or south. Right now the sun is moving
    north at a rate of 0.2 knots."
    
    No, the Sun has picked up Northerly speed since midwinter and right now is
    moving North at just over 0.6 knots.
    
    ================
    
    All this complication demonstrates the futility of trying to obtain a
    precise longitude from Sun observations made anywhere near noon. Noon is
    the time for measuring latitude, as navigators have traditionally done
    throughout history. Longitude is best measured by Sun altitude observations
    taken well away from noon, in early morning or late afternoon, as
    navigators have traditionally done ever since longitude measurement became
    possible.
    
    George.
    
    contact George Huxtable, at  george{at}hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
    
    
    

       
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