FWCONV-General unit conversion for spectra

Description:

FWCONV converts the flux units of a spectrum from AB magnitudes, Janskys, milli-Janskys, micro-Janskys or erg/s/cm**2/A to any of these.

Parameters:

SPECTRUM

A spectrum whose units are either Janskys, milli-Janskys, micro-Janskys, erg/s/cm**2/A or AB magnitudes.

FLUX_UNIT

Units of either Janskys, milli-Janskys, micro-Janskys, erg/s/cm**2/A or AB magnitudes.

OUTPUT

The resulting spectrum, whose units will be either Janskys, milli-Janskys, micro-Janskys, erg/s/cm**2/A or AB magnitudes. OUTPUT can be the same as SPECTRUM, in which case the conversion will be performed in situ.

Source comments:

 F W C O N V

 Converts flux units of a spectrum from/to either
 F_lambda (ergs/sec/cm**2/A), AB magnitudes or F_nu (Janskys).

 Command parameters -

 SPECTRUM The name of the structure containing the spectrum.
          An x-axis data structure giving the wavelengths of the
          data elements is also required.

 OUTPUT   The name of the result of the operation.  This can
          be the same as for SPECTRUM. If not, a new structure
          is created, with everything but the data a direct
          copy of the input.

 Command keywords  - None

 User variables used - None

 4th  Feb 1991.  SMH/ AAO.  Original version, based on ABCONV code,