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    Venus with Earth Oblateness - 3rd time a charm?
    From: Michael Dorl
    Date: 2004 Oct 13, 15:09 -0500

    I guess I did it again, my help desk says things should be better now.
    Hopefully no html aka 'styled text'
    
    Michael
    
    =========
    
    Here are the details on the calculation of TPC for Geocentric coordinates
    from Mosier's
    routines for Venus and the Moon
    
    11/9/2004
    11:13:05
    dt = 64.4 seconds
    temp = 5Cpressure 1010 MB
    elevation 294M
    
                                                     Venus
    Moon
    
    geocentric RA                       10h34m45.1022s           9h37m13.8949s
    diurnal aberration                 0.0076s                           0.0113s
    dirunal
    parallax                      0.3498s                          2m7.3158s
    refraction                               -5.6126s
    -3.2805s
    tpc RA                                   10h34m39.8470s           9h39m17.9415s
    
    geocentric DECL                  9d40'04.3470'"               19d29'00.7421"
    diurnal aberration                -0.0346"                          -0.0573"
    diurnal
    parallax                    -4.8748"                          -26'23.5639"
    refraction                               1'18.7829s
    41.3482"
    tpc
    DECL                               9d41'18.2205"                19d3'18.4692"
    
    I can supply the details on the J2000 to Geocentric transformation if that
    would help but  I think we are agreed on the Geocentric position.
    
    Calculating Venus/Moon Ctr/Ctr distance from TPC coordinates, one gets
    16d20'22.16".  Assuming Moon semi-diameter of 15'3.876" gives distance from
    Venus to Moon limb of 16d05'18.284" = 16d05.3".
    
    As far as I can tell there is nothing in the routines to allow for
    oblateness of the earth. One can specify a elevation. Looks like the earth
    is assumed to have a radius of 6378137 Meters, same as equatorial radius in
    my 1988 AA page K6.
    
    If I include an elevation of -9600 meters, I get a ctr/ctr distance of
    16d20'25.88". Taking off a  moon semi-diameter of 15'3.88" gives a ctr to
    limb distance of 16d5'22" or 16d5.37' which is close to Frank's 16d5.5'. I
    got the -9600 meters by considering the earth to be an oblate spheroid. I
    think Mosier considers the earth to have an equatorial radius so setting
    the elevation negative should compensate for the oblateness.
    
    Michael
    
    
    

       
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