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    Re: Refraction, Cassini model
    From: Paul Hirose
    Date: 2018 Nov 28, 15:33 -0800

    On 2018-11-27 18:45, Roger W. Sinnott wrote:
    > By the way, the latest (3rd ed., 2013) of the Explanatory Supplement to the 
    Astronomical Almanac, on pages 277-280, gives a number of methods for finding 
    the atmospheric refraction.  Along with several low-accuracy formulas, it 
    describes a precise algorithm for calculating refraction using numerical 
    integration.  This method is written out in clear steps, like the outline of 
    a computer program.
    
    That last sounds like the algorithm in the 1992 Explanatory Supplement.
    Andrew Young (not Bruce Young as I originally wrote — thank you for the
    correction) criticizes its refractive index formulas:
    
    "Unfortunately, this incorrect and obsolete formula was also used by
    Hohenkerk & Sinclair (1985), from which it was copied in the new (1992)
    edition of the Explanatory Supplement (see the middle of p. 142 for the
    obsolete formula there); so we can expect to continue to see it crop up
    again in the future."
    
    https://aty.sdsu.edu/explain/atmos_refr/air_refr.html
    
    The 1985 Hohenkerk and Sinclair work was Nautical Almanac Technical Note
    63, "The computation of angular atmospheric refraction at large zenith
    angles."
    
    http://astro.ukho.gov.uk/nao/technotes/
    
    Young notes some issues with that document:
    
    https://aty.sdsu.edu/bibliog/bibliog.html#Hohenkerk+Sinclair1985q
    
    In the Technical Note I discovered some trivia about the Nautical
    Almanac: the low altitude refraction table was computed with the 1944
    model of Garfinkel:
    
    
    http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1944AJ.....50..169G&db_key=AST&page_ind=0&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES
    

       
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