NOTE: These are the previous versions where the data and headers are all in
one structure, but with webget replaced by IDLnetURL in query_irsa_cat.pro 
(note added Aug 2017).

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CONTENTS
-------------

4 IDL programs are provided:
     query_irsa_cat.pro   --  query IRSA catalogs from the IDL command line (returns a structure)
     read_ipac_table.pro  --  read an IPAC table from a file into IDL (returns a structure)
     read_ipac_var.pro    --  read an IPAC table from an internal IDL variable (returns a structure) - used by query_irsa_cat.pro
     write_ipac_table.pro --  write an IDL structure into an IPAC ascii table file

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INSTALLATION REQUIREMENTS
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--- Latest IDLASTRO

Make sure you have the latest versions and that they are in your IDL path.  See:

https://idlastro.gsfc.nasa.gov/contents.html

--- Programs in PATH

Put the programs in the IDL path.

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USAGE EXAMPLE
-------------

IDL> .run read_ipac_var.pro,query_irsa_cat.pro
IDL> info = query_irsa_cat([150.11917,2.205833], catalog='irasfsc', radius=1, radunits='deg')

QUERY_IRSA_CAT.pro performs a query of a catalog in the IRSA holdings.
The default is to query the 2MASS Point Source Catalog ('fp_psc').  It
returns an IDL structure containing the contents of the downloaded
table. If "outfile" is present, it will write the incoming table to a
file.  This can be slow, so only do so if needed.

Queries can by made by RA,Dec or by object name (resolved by NED
or SIMBAD).  The radius of the search may be specified; the default
units are arcsec.  See the file header for further details.

In order to query other IRSA catalogs, the program needs to know
the identifier string for the IRSA Program Interface.  The complete
list of current catalogs (with the needed string) is available in 
XML format at

https://irsa.ipac.caltech.edu/cgi-bin/Gator/nph-scan?mode=xml

or as an IPAC Table (ascii) at

https://irsa.ipac.caltech.edu/cgi-bin/Gator/nph-scan?mode=ascii

The identifier string needed for the IDL program is the "catname"
column of the table.

Notes on usage for the other programs are in the file headers.
