Purpose: IDL procedure to calculate source coordinates as seen by an observatory correcting for annual parallax and proper motion.

Author: S. Carey (SSC)
Date Contributed 12 Feb 2013 (Revised 25 Oct 2016 to update ephemerides with dates through 2019)
System Requirements: IDL (tested on IDL 8.1)

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Determine astrometric position in Equatorial (J2000) coodinates for an object given the position at a previous epoch, the proper motion and the annual parallax. Designed for refining coordinates for Spitzer observations.