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    Re: Definition of the twilight intervals
    From: Andrés Ruiz
    Date: 2015 Aug 18, 09:28 +0200
    When your eye see the UL of the Sun kissing the horizon Hs = 0º and Ho = -50', mainly due to refraction.

    An example:

    18/05/2015
    19:28:07 UT1
     
    NAUTICAL ALMANAC
    Sun
    GHA = 112.923932 º = 112º 55.4'
    Dec = 19.607304 º =  19º 36.4'
    SD = 15.8111 '
    HP = 0.1449 '
     
    ALTITUDE CORRECTION
    Limb: upper
    Ref: SeaHorizon
    Hs = 0.0000 º =   0º  0.0'
    ic = 0.0000 '
    heas = 0.0000 m
    T = 10.0 ºC
    P = 1010.0 hPa
    Hoi = 0.0000 º
    dip = 0.0000 º
    Ha = 0.0000 º =   0º  0.0'
    R = 0.5743 º
    OB = -0.00000381 º
    HP = 0.0024 º
    PA = 0.00241106 º
    SD = -0.2635 º
    Aug = 0.00000000 º
    SDag = -15.81110882 '
    Ho = -0.8354 º = -  0º 50.1'

    Sometimes definitions depend on the sources.
    Peace sells but who's buying.
    Regards,
    --
    Andrés Ruiz
    Navigational Algorithms
    http://sites.google.com/site/navigationalalgorithms/
       
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