PHOTCAL

Name

photcal

Purpose (one Line Only)

Photometric calibration using two lists of partially overlapping sources.

Description

Calling Sequence

photcal,ra,dec,imag,imagerr,catra,catdec,catmag,ngood,photzp,
photzperr,magrange

Inputs

ra - J2000 right ascension of source (usually from a CCD image)
dec - J2000 declination of source (usually from a CCD image)
imag - instrumental magnitude
imagerr - uncertainty on the instrument magnitude
catra - J2000 right ascension of the catalog (known) source.
catdec - J2000 declination of the catalog (known) source.
catmag - Standard catalog magnitude
catmagerr - Uncertainty of the standard catalog magnitude

Optional Input Parameters

Keyword Input Parameters

MAXSEP - Maximum allowable separation in arcseconds between sources in the
two lists that will be considered a match (default=1.5 arcsec).
NODISPLAY - Flag, if set will suppress all plots
UNIQUE - Flag, if set will force the linking of the two lists to be
a one-to-one mapping.
RETURN_ALL - Flag, if set will return all cross-correlated sources.
Normally, those that are marked as bad are removed from
INDEX1 and INDEX2 before returning. If you want them
all for some other external processing you will set this.

Outputs

ngood - Number of good matches
photzp - Photometric zero-point that when added to the instrumental
magnitude will return the standard magnitude in the system
of the catalog.
photzperr - Uncertainty on the zero-point
magrange - magnitude range of the catalog stars used, 2-element vector
with [faintmag,brightmag]

Keyword Output Parameters

BAD - Bad flag array, same length as the input arrays.
INDEX1 - index into catalog list for the matched list of good stars
INDEX2 - index into star list for the matched list of good stars

Common Blocks

Side Effects

Restrictions

Procedure

Modification History

Written by Marc W. Buie, Lowell Observatory, 2007/02/01
2008/08/07, MWB, added MAXSEP, UNIQUE, and NODISPLAY keywords
2011/04/25, MWB, added RETURN_ALL and BAD keywwords