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    Dip
    From: Alexandre Eremenko
    Date: 2004 Nov 27, 18:41 -0500

    Dear fellow list members,
    
    I recently found an atricle which seems
    very disturbing to me:
    "Refraction near the horizon" by Schaefer and Liller,
    Publ. Astr. Soc. Pacific.
    You can read the paper on
    http://www.math.purdue.edu/~eremenko/dip.pdf
    The main point of the article is that the refraction
    near the horizon (and thus the dip of the horizon)
    varies unpredictably and the variation is enormous.
    
    The authors do not discuss Cel Nav in this paper,
    their main concern is refuring "Archaeoastronomy".
    
    I don't care about Archaeoastronomy, but their main
    conclusions seem to imply that the refraction
    near the horizon (and thus the dip) is uncertain
    to more than 1/2 of a degree.
    
    Then how is traditional CelNav based on altitude measurements
    possible at all?
    
    Any comments?
    
    Alex.
    
    
    

       
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