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    Re: Any "on line" Star Position Computation available ?
    From: Paul Hirose
    Date: 2011 Jun 15, 11:17 -0700

    ICRS coordinates of Diphda at epoch J2000.0:
    
    00 43 35.371451  -17 59 11.77811  FK6 (VizieR) [1]
    00 43 35.22827   -17 59 12.0627   HIP2 (SIMBAD) [2]
    00 43 35.3709    -17 59 11.783    HIP2 (Hirose) [3]
           -------           ------
             .143s             .28"    SIMBAD - Hirose
    
    [1] The FK6 catalog values don't require any correction for epoch or
    reference frame.
    
    [2] The Hipparcos catalogs (the original reduction and the improved 2007
    reduction) give the ICRS position at epoch J1991.25. The coordinates on
    this line are the SIMBAD's adjustment to epoch J2000.0.
    
    [3] Hipparcos second reduction (2007) coordinates from VizieR,
    transformed from epoch J1991.25 to J2000.0 by Hirose.
    
    
    As Kermit already observed, the SIMBAD coordinates don't agree with the
    others. Why? I think SIMBAD applied the proper motion correction twice.
    Look at the corrections to transform from 1991.25 to 2000.0 (HIP2 values):
    
    232.55 mas/yr * 8.75 yr / cos dec = 2140 mas = .143s
    31.99 mas/yr * 8.75 yr = 280 mas = .28"
    
    These values are identical to the anomalies in the SIMBAD coordinates.
    
    --
    I filter out messages with attachments or HTML.
    
    
    
    

       
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