idlastro / DAOPHOT-Type Photometry Procedures: T_GETPSF

[Source code]

NAME
T_GETPSF
PURPOSE
Driver procedure (for GETPSF) to generate a PSF from isolate stars.
EXPLANATION
Generates a point-spread function from one or more isolated stars.
List of stars is read from the FITS ASCII table output of T_APER.
PSF is represented as a sum of a Gaussian plus residuals.
Ouput residuals are written to a FITS image file.
CALLING SEQUENCE
T_GETPSF, image, fitsfile, [ idpsf, psfrad, fitrad, psfname, 
                                /DEBUG, NEWTABLE =]
INPUTS
IMAGE - image array
FITSFILE  - scalar string giving name of disk FITS ASCII table.  Must 
        contain the keywords 'X','Y' (from T_FIND) and 'AP1_MAG','SKY'
        (from T_APER).
OPTIONAL INPUTS
IDPSF - vector of stellar ID indices indicating which stars are to be 
        used to create the PSF.    Not that the PSF star should be 
        specified *not* by its STAR_ID value, but rather by the its 
        row number (starting with 0) in the FITS table
PSFRAD - the radius for which the PSF will be defined
FITRAD - fitting radius, always smaller than PSFRAD
PSFNAME - name of FITS image file to contain PSF residuals,
        scalar string
GETPSF will prompt for all the above values if not supplied.
OPTIONAL KEYWORD INPUT
NEWTABLE - scalar string specifying the name of the output FITS ASCII
        table.   If not supplied, then the input table is updated with
        the keyword PSF_CODE, specifying which stars were used for the
        PSF.
DEBUG - if this keyword is set and non-zero, then the result of each
        fitting iteration will be displayed.
PROMPTS
T_GETPSF will prompt for the readout noise (in data numbers), and
the gain (in photons or electrons per data number) so that pixels can
be weighted during the PSF fit.   To avoid the prompt, add the 
keywords RONOIS and PHPADU to the FITS ASCII table header.     
PROCEDURES USED
FTADDCOL, FTGET(), FTPUT, GETPSF, READFITS(), SXADDHIST, SXADDPAR, 
SXPAR(), WRITEFITS, ZPARCHECK
REVISION HISTORY
Written  W. Landsman     STX           May, 1988
Update PSF_CODE to indicate PSF stars in order used, W. Landsman Mar 96
I/O to FITS ASCII disk files  W. Landsman    May 96
Converted to IDL V5.0   W. Landsman   September 1997
Update for new FTINFO call   W. Landsman   May 2000