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    Star proper motion
    From: Aubrey O´Callaghan
    Date: 2001 Nov 20, 7:04 AM

    I am astro navigation writing some software for my HP49G and have been
    looking for star proper motions for calculation of SHA.
    I have found a good website (http://www.alcyone.de/SIT/SIT_en.htm). However
    I have some questions about the proper motion.
    Looking up the proper motion of Sirius
    (http://www.alcyone.de/SIT/mainstars/SIT000499.htm) get some conflicting
    answers depending upon the source, which should be used to get the Nautical
    almanac equivalent ?
    
    I can live with the difference is the RA and the declination. However I
    find an order of magnitude of difference in the RA proper motion
    disconcerting. The Bright Star catalogue and the Washington Visual Double
    star catalogue give the same values but the SKY200 0 Master Star Catalog
    and Smithsonian Astrophysical Observatory Star Catalog give another value
    
    The SKY2000 Master Star catalogue references its source of proper motion to
    "The Bright Star Calalogue, yet gives a different answer to the Bright Star
    catalogue".
    I get similar results when I look up Procyon, so I don't believe in typo
    errors. Does anybody have an explanation ?
    
    Aubrey.
    
    The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version)
    (Hoffleit+, 1991)
    Position (J2000) RA 6h 45min 8.9sec Dec -16 42' 58"
    Proper motion   RA -.553 arcsec/a  Dec -1.205 arcsec/a
    
    data from SKY2000 - Master Star Catalog (Myers+ 1997)
    Position (J2000) RA 6h 45 min 8.821sec  Dec -16 42' 56.85"
    Proper motion -0.0385 arc/a  Dec -1.205 arcsec/a
    
    data from Smithsonian Astrophysical Observatory Star Catalog (SAO Staff
    1966; USNO, ADC 1990)
    Position (J2000) RA 6h 45min 8.917sec  Dec -16 42' 58.11"
    Proper Motion -.0379 arcsec/a Dec -1.206 arecsec/a
    
    data from The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996)
    Position (J2000) RA 6h 45.1   Dec -16 43 min
    Proper Motion -0.553 arcsec/a Dec 0 arecsec/a
    

       
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