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   Reduction of stellar coordinates to apparent coordinates. Includes
   corrections for
   - radial velocity of star
   - parallax
   - gravitational light deflection
   - relativistic aberration due to earth and spacecraft velocity
   - Earth precession and nutation   
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   Form:
   u = SReduce( rA0, dec0, pMRA, pMDec, parallax, rV, vSc, jD )
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   Inputs
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   rA0           (1,1)      Catalog right ascension
   dec0          (1,1)      Catalog declination
   pMRA          (1,1)      Proper motion in right ascension   
   pMDec         (1,1)      Proper motion in declination
   parallax      (1,1)      Stellar parallax
   rV            (1,1)      Radial velocity (km/sec)
   vSc           (1,1)      Spacecraft velocity vector (km/sec)
   jD            (1,1)      Julian date 

   -------
   Outputs
   -------
   u             (3,1)     Unit vector

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