HFWG Recommendation R4:

        On the use of the CATIDn FITS keywords to contain 
                  source catalog identifications

                     (Approved: 1993 Aug 04)


It is recommended that source identifications be coded using the
following character-valued keywords:

	CATIDn

where n is an integer index in the range 1 - 9.

It should be stressed that the CATIDn keyword augments, rather than
replaces, the standard OBJECT keyword.  Furthermore, when indexed, the
CATIDn keywords should only be used to give alternative identifications
to the SAME source.  It is NOT to be used to give identifications to
multiple sources in a given observation.

Users are encouraged to use catalog abbreviations as given in the
current version of 'The First Dictionary of Nomenclature of Celestial
Objects' (Fernandez, Lortet & Spite 1983), it's first supplement
(Lortet & Spite 1986), and any future supplements.  COMMENT cards
should translate any abbreviation which are used for catalogs not
listed in these articles. Catalog abbreviations should be given with
spaces replaced by underscores; one or more spaces should separate the
catalog abbreviation from the source entry in the catalog.  Ancilliary
information such as the reference to the catalog can, of course, be
embedded in COMMENT cards.

Examples of Usage

Example 1

CATID1  = 'HD 153919'          / identification of source
COMMENT   Henry Draper Catalog, Cannon, A., 1925 HCO

Example 2

CATID1  = 'MPSLX 3'             / identification of source
COMMENT   MPSLX: The ROSAT MERGED SOURCE LIST for pointing
CATID2  = 'HD 153919'           / alternative identification of source
COMMENT   Henry Draper Catalog, Cannon, A., 1925 HCO
CATID3  = '4U 1700-37'          / alternative identification of source
COMMENT   4th Uhuru catalog

Example 3

OBJECT  = 'NORTH ECLIPTIC POLE'
CATID1  = 'MPLSX 5'            / identification of source
COMMENT   MPSLX: The ROSAT MERGED SOURCE LIST for pointing