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    GHA Aries and GHA and Declination of the Sun
    From: Bill Murdoch
    Date: 1997 Dec 17, 9:35 PM

    Woops.  There is a mistake in the date part of the GHA Aries and sun GHA and
    declination calculation forms that I posted a week or two ago.  I slipped up.
    The year 2000 is a leap year, so an extra day of 86,400 seconds has to be
    inserted after February 29.  I modified the form and a new copy is attached.
    If you find any other mistakes, let me know.
    
    For someone who wants to put the formulas a program, there is an easy way to
    convert customary time and date to centuries before and after 1200 1 Jan 2000.
    It comes from Van Flandern and Pulkkinen, Low Precision Formulae for Planetary
    Positions, The Astrophysical Journal Supplement Series, vol 41, p 391, (1979).
    It works from March 1900 through February 2100.  They also have another
    formula for longer lengths of time.
    
    T = (367*yr-trunc(7*(yr+trunc((mo+9)/12))/4)
         +trunc(275*mo/9)+day+(hr+(min+sec/60)/60)/24
          -730531.5)/36525
    
    The function trunc is just like trunc in Excel.  It drops the fractional part
    of the number.
      trunc(8.9) = 8,
      trunc(-8.9) = -8.
    
    Bill Murdoch
    Kingsport, Tenn.
    

       
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