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    Re: 18 june 2013 lunar distance
    From: Paul Hirose
    Date: 2013 Jul 03, 12:53 -0700

    Antoine Couëtte wrote:
    > In RE# 1, for (apparently) exactly the same date and time "[2013-06-18 0330 
    UT1, 67.1178 delta T, DE406 ephemeris, Hipparcos second reduction]" I can 
    read that you published the Moon and Altair coordinates as follows :
    >
    > QUOTE
    >
    > From Lunar3 I get Moon coordinates
    >
    > -2.44969548e-003 -5.24187596e-004 -3.58294080e-004 au, or
    > 192° 04′ 40.973″  -08° 08′ 21.886″
    >
    > and Altair coordinates
    > 4.59325899e-001 -8.74784757e-001 1.54179599e-001 au, or
    > 297° 42′ 09.913″  +08° 52′ 09.188″
    >
    > UNQUOTE
    >
    > I can see that both sets of results are quite different.
    
    Thank you for the reply, Kermit. The part you did not quote explains the
    mystery: "And to eliminate any question about the precession / nutation
    model, I wonder if Dave can put the coordinates in the GCRS. From Lunar3
    I get Moon coordinates..."
    
    So the coordinates above are in the GCRS, not the true equator / equinox
    system. For the latter, computed with the IAU 2006 / 2000A precession
    nutation model, Lunar3 says,
    
    12h49m01.4774s  -8°12′48.749″  Moon
    19h51m28.2889s  +8°54′23.396″  Altair
    
    As a check, the separation angle between those coordinates should be the
    same as the angle computed from the GCRS coordinates. I get 106 34
    28.454, only 1 mas greater. From your coordinates I compute 106 34 29.454.
    
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