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Coordinate Keywords used in MAST FITS Files

In general, data sets archived within MAST use Right Ascension and Declination to specify target coordinates, although the keywords used to designate the coordinates vary. The table below summarizes these differences. For more information on file formats, click on the mission names.

Mission Coordinate Keywords* Equinox Units
Copernicus RA-DEGS 2000 decimal degrees
BEFS RA_OBJ 2000 decimal degrees
EUVE RA_OBJ, RA_PNT 2000 decimal degrees
FUSE RA_APER, RA_TARG 2000 decimal degrees
HUT (none) - -
IMAPS RA 2000 decimal degrees
IUE LRA, SRA, LTARGRA, STARGRA 1950 decimal degrees
UIT NOMRA 1950/2000 decimal degrees
WUPPE RA 1950 decimal degrees

*Keyword Explanation:

  • RA-DEGS- RA in degrees,
  • RA_OBJ - RA of object (provided by Guest Observer),
  • RA_PNT- RA of pointing (indicates slight offset needed for EUVE observations),
  • RA_APER- RA at center of aperture,
  • RA_TARG- RA of target,
  • LRA,SRA- IUE Large and Small Aperture RA (homogeneous coordinates derived from Simbad),
  • LTARGRA,STARGRA- IUE Large and Small Aperture RA provided by Guest Observer,
  • NOMRA- UIT nominal RA
Note that data sets containing images (e.g., UIT) also provided coordinates using CRVALn keywords.