CO_ABERRATION

     Calculate changes to Ra and Dec due to "the effect of aberration",

      as described in Meeus, Chap 23.

      co_aberration, jd, ra, dec, d_ra, d_dec, [EPS = ]

       jd      : Julian Date [scalar or vector]
       ra, dec : Arrays (or scalars) of the ra  and dec's in degrees
   Note: if jd is a vector, ra and dec MUST be vectors of the same length.

       d_ra, d_dec: the corrections to ra and dec due to aberration (must then
                     be added to ra and dec to get corrected values).

       eps : set this to the true obliquity of the ecliptic (in radians), or
         it will be set for you if you don't know it (in that case, set it to
                 an empty variable).

   Compute the change in RA and Dec of Theta Persei (RA = 2h46m,11.331s, Dec =
   49d20',54.54" on 2028 Nov 13.19 TD
      IDL> jdcnv,2028,11,13,.19*24,jd      ;Get Julian date
      IDL> co_aberration,jd,ten(2,46,11.331)*15,ten(49,20,54.54),d_ra,d_dec
      ==> d_ra = 30.045"    d_dec = 6.697"

  These formula are from Meeus, Chapters 23.  Accuracy is much better than 1
   arcsecond.

   Written, June 2002,      Chris O'Dell, U. of Wisconsin

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