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    Re: Moonrise over Connecticut, 19 October 2021
    From: Antoine Couëtte
    Date: 2021 Oct 29, 12:11 -0700

    Frank,

    In further reference to my earlier post to which you just replied here, - thanks for your quite detailed reply - let's again take a look at the the USNO Web Application clone following results:

    Celestial Navigation Data for 2021 Oct 19 at 21:59:27 UT           
                                                                                   
                     For Assumed Position:  Latitude    N 41 18.4                 
                                            Longitude   W 72 30.0                 
                                                                                   
                            Almanac Data                |    Altitude Corrections  
     Object       GHA        Dec         Hc       Zn    |   Refr   SD    PA    Sum 
                  o   '      o   '      o   '       o   |     '     '     '     '  
     SUN        153 39.1   S10 18.4   - 0 15.2   256.4  |  -31.0  16.1   0.1 -14.8 
     MOON       339 48.3   N 4 02.6   + 0 38.9    85.2  |  -24.0  15.0  55.2  46.2 
     VENUS      106 55.5   S25 40.0   +15 49.0   212.0  |   -3.4   0.0   0.2  -3.2 
     JUPITER     33 22.6   S15 08.8   +22 57.4   138.6  |   -2.3   0.0   0.0  -2.3 
     SATURN      48 53.7   S19 19.7   +25 32.1   155.2  |   -2.0   0.0   0.0  -2.0 
     ARIES      358 27.2                                                           
    
                     Moon phase is waxing,  99% illuminated.

    there is a definite refraction correction error for the Moon which should show -31.0' exactly like for the Sun, instead of currently showing -24.0' .

    As earlier surmised, the Moon refraction Correction showing up as " -24.0 " is the Inverse Refraction - actually the right refraction function to be used in such reverse engineering - applied by error to the Geocentric Height "Hc" while it should be applied to the Topocentric unrefracted height.

    BODY

    Hc

    Inverse refraction

    from Éphémérides Nautiques

    Published Refr in

    USNO Web Application clone

    SUN

    -0°15.2’

    -30.04’

    -31.0’

    MOON

    +0°38.9’

    -24.03’

    -24.0’

    VENUS

    +15°49.0’

    -3.37’

    -3.4’

    JUPITER

    +22°57.4’

    -2.27’

    -2.3’

    SATURN

    +25°32.1’

    -2.01’

    -2.0’

    As earlier surmised, this mismatch is only visible onto Low Alt Bodies with a significant HP, in other words, it is only visible for Lady Moon quite close from the Horizon.

    Hence it fully explains why the example you just published shows a perfect match between the former USNO Web Application and the current USNO Web Application clone since Lady Moon height is about 25° in it.

    This bug should be very simple and straightforward to correct : simply apply Inv (Ref) to Topocentric Height vs. Geocentric height.

    Hope it helps !

    Antoine M. "Kermit" Couëtte

    antoine.m.couette[at]club-internet.fr

       
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