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    Re: 1901 May, 22 Lunar example by French Navy Captain Arago
    From: Paul Hirose
    Date: 2010 Feb 24, 23:13 -0800

    Antoine Couette wrote:
    > To help me here, just be so kind as to indicate to me which Precession 
    > data set you are currently using in your software (I would be guessing 
    > that you might be using our current (is it 2002 ? or rather 2004 ?) IAU 
    > recommended values.
    
    In 2006 the IAU recommended a new precession / nutation model, to go
    into effect in 2009:
    http://www.iau.org/static/resolutions/IAU2006_Resol1.pdf
    
    I use the SOFA implementation:
    http://www.iausofa.org/2009_0201_F/sofa/pnm06a.html
    
    It generates a rotation matrix to convert a vector from the GCRS to the
    true equator and equinox of date, with IAU 2006 precession / nutation.
    
    
    Coordinates of kappa Cancri at your immersion time:
    
    1901-03-02T22:43:32.30 Terrestrial Time
    1901-03-02T22:43:33.40 UT1
    -1.10 delta T (TT-UT1)
    
    observer position
    +48°23'30.0" -  4°29'31.2"  N lat, E lon
    0 m (0 ft) above ellipsoid
    
    kappa Cancri = name of body
    
    Barycentric right ascension and declination in the ICRS. These are the
    ICRS coordinates at the occultation time. I.e., they are the Hipparcos
    catalog coordinates adjusted for proper motion. At .1" accuracy, there
    is no significant difference between the ICRS (or GCRS) and the J2000
    mean equator and equinox.
      9h07m44.95s +10°40'06.5"  RA, dec
    
    Geocentric apparent coordinates in the GCRS. These are the above
    coordinates plus aberration. Parallax is insignificant for this star.
      9h07m46.13s +10°40'00.2"  RA, dec
    
    Geocentric apparent coordinates with respect to the true equator and
    equinox at the occultation time. These are the above coords, plus IAU
    2006 precession / nutation.
      9h02m25.79s +11°03'44.2"  RA (equinox), dec
    
    Unrefracted topocentric coordinates. These are the above coordinates
    plus dinural aberration, and converted to the observer's horizontal
    coordinate system.
    181°18'44.6"  52°39'52.0"  37°20'08.0"  az, el, ZD
    
    
    Here are values from the USNO MICA 2.0 program.
    
    geocentric apparent (true equator of date)
      9h02m25.771s +11°03'44.30"  RA, dec
    
    unrefracted topocentric
    181°18'44.7" 37°20'07.9"  az, zenith distance
    
    MICA uses the IAU 1976 precession and 1980 nutation.
    
    -- 
    I filter out messages with attachments or HTML.
    
    
    

       
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