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    Re: Venus phase correction
    From: Antoine Couëtte
    Date: 2018 Sep 23, 10:22 -0700

    RE : Venus-phase-correction-Bernecky-sep-2018-g42825

    Dear Robert,

    What a small world !

    Thank you very much for your detailed and very impressive work.


    I just submitted to NavList a reply to Paul Hirose - just published as: Unexpected-USNO-height-correction-precepts-Couëtte-sep-2018-g42827 - and in which I mentioned :


    I am using our most regretted George Huxtable's recommended formula published in NavList [11961] on Sep 18th, 2010.

    Let SD be the angular semi-diameter seen from Earth center, "φthe phase angle, then the phase correction "λ" is computed as follows :

    λ = [ 8 / (3π) ] * sin² (φ/2) * SD

    1.b - Numerical Application

    As per your request here-under, I am giving here-after extra digits to 0.01' to be sure that round off errors do not "contaminate" this numerical example, although extra-digits are not really necessary in this specific example.

    - Venus semi-diameter : 0.42'

    As a numerical application, with φ139° as stated in your second post referenced here-under, then λ = [ 8 / 9.425... ] * sin² (139°/2) * 0.42' = 0.31' .



    You had the kindness of using my Venus Example of March 18, 1977 and you found : δ GHA= +0.265' and δ DEC = -0.185'

    My own results are extremely close from yours with : δ GHA= +0.263' and δ DEC = -0.184'  which boil down into δ  Height = +0.31' in this specific example as mentioned here-above.

    Looks like your own computation results fully confirm the results published by George Huxtable. Excellent !  :-)

    Nice work and well done !

    Very Best Regards,

    Antoine M. "Kermit" Couëtte

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