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    Almanac accuracy, WAS: Re: Hughes Tables.
    From: Peter Hakel
    Date: 2009 Jul 17, 10:20 -0700
    From two independent sources I find the GP of Fomalhaut at this time as:

    GHA:   82 degrees 04.8'
    Dec:  S 29 degrees 34.4'

    I am still learning what degree of accuracy one might realistically expect from different sources of astronomical data.  I remember reading that almanacs are only guaranteed to about 0.3', so the declination values are not too far off from each other.  The GHAs differ by more than I would expect.  Any comments?  I assume that this difference in GHA is inherited from the star's SHA, since GHA Aries is relatively straightforward to calculate.  So, for completeness:

    GHA Aries: 66 degrees 37.1'  (the other source gives 37.0')
    SHA:           15 degrees 27.7'


    Peter Hakel

    ==== Begin quoted message fragment ====

    You gave Lat 40 N.  Long 77W. fomalhault  on 13th July 2009 at 09-00Hrs.

    I found the following:-

    Using ICE 0.51 for the ephemeris data for formalhaut for 13th July 2008 09-00Hrs:-

    GHA is 81-49.6
    Dec is S. 29-34.0    (N.B. ICE gives an Hc for the Lat40  Long 77W of 20-17.3)



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