
addstar is expecting to get the following information from the header.

Required keywords:

NAXIS1, NAXIS2
NASTRO (non-zero for valid astrometry solution)
NSTARS 
CERROR (astrometric error)

a valid WCS:

CTYPE1,2
CRVAL1,2
CRPIX1,2
CDELT1,2
PC001001
PC001002
PC002001
PC002002

PHOTCODE

optional keywords:

APMIFIT, dAPMIFIT
FLIMIT, FSATUR
FWHM_X, FWHM_Y, 
TRATE (for driftscanning)
ZERO_PT 

Note that these entries are used to define the actual keywords:

(eg, in the dvo.config file, DATE-KEYWORD tells addstar what keyword
to use for the DATE).

For Date/Time, one of the following three sets is needed:

 * DATE-KEYWORD (date in format specified below)
 * DATE-MODE (YYYY/MM/DD, MM/DD/YYYY, DD/MM/YYYY)
 * UT-KEYWORD (HH:MM:SS for UT)

 or:

 * MJD-KEYWORD (MJD)

 or: 

 * JD-KEYWORD (JD)

For Exposure time:

 * EXPTIME-KEYWORD (seconds)

For Airmass:

 * AIRMASS-KEYWORD

CCDNUM-KEYWORD??

For sidereal time (optional):

 * ST-KEYWORD

For alternate EXTNAME:

 * EXTNAME-KEYWORD

