DEFINE FITS

        DEFINE FITS Var File [/GLOBAL]

    defines variables associated to the keywords and data of  a  FITS  file.
    The defined variables depend on the FITS file content. Both "basic" FITS
    files and FITS extension (XTENSION) are handled.

    For basic FITS data, the following variables are defined

       VAR%NDIM       Integer        Number of dimensions
       VAR%DIM        Integer[4]     Dimensions
       VAR%CONVERT    Double[3,4]    Conversion formulae for the 4 axes:
                                     Reference pixel,
                                     Value at reference pixel,
                                     Increment
       VAR%DATA       Real           FITS data array
    The variables are defined as part of a structure.  GreG  command  LIMITS
    /RGDATA A recognizes such a basic FITS structure in much the same way as
    GILDAS images.

    The DEFINE FITS command tries to define a SIC structure  which  contains
    all  FITS  keywords,  as  well as all binary and ASCII tables located in
    FITS  extensions.  Support  for  Random  groups  (an  obsolescent   FITS
    structure) is not implemented.

    DEFINE FITS only works to read FITS files, but not to create them.