idlastro / DAOPHOT-Type Photometry Procedures: T_APER

[Source code]

NAME
T_APER
PURPOSE
Driver procedure (for APER) to compute concentric aperture photometry.
EXPLANATION
Data is read from and written to disk FITS ASCII tables.   
Part of the IDL-DAOPHOT photometry sequence
CALLING SEQUENCE
T_APER, image, fitsfile, [ apr, skyrad, badpix, PRINT=, NEWTABLE=, 
                /EXACT, /SILENT, SETSKYVAL = ]
INPUTS
IMAGE   - input data array
FITSFILE  - disk FITS ASCII table name (from T_FIND).  Must contain
        the keywords 'X' and 'Y' giving the centroid of the source
        positions in FORTRAN (first pixel is 1) convention.   An
        extension of .fit is assumed if not supplied.
OPTIONAL INPUTS
User will be prompted for the following parameters if not supplied.
APR    -  Vector of up to 12 REAL photometry aperture radii.
SKYRAD  - Two element vector giving the inner and outer radii
        to be used for the sky annulus
BADPIX  - Two element vector giving the minimum and maximum
        value of a good pixel (Default [-32765,32767])
OPTIONAL KEYWORDS INPUTS
/EXACT - If this keyword is set, then intersection of the circular
        aperture is computed exactly (and slowly) rather than using
        an approximation.   See APER for more info.
/PRINT - if set and non-zero then NSTAR will also write its results to
        a file aper.prt.   One can specify a different output file 
        name by setting PRINT = 'filename'.
/SILENT - If this keyword is set and non-zero, then APER will not
        display photometry results at the screen, and the results 
        will be automatically incorporated in the FITS table without
        prompting the user
NEWTABLE  - Name of output disk FITS ASCII table, scalar string.   
        If not supplied, then the input FITSFILE will be updated with 
        the aperture photometry results.
SETSKYVAL - Use this keyword to force the sky to a specified value 
        rather than have APER compute a sky value.    SETSKYVAL 
        can either be a scalar specifying the sky value to use for 
        all sources, or a 3 element vector specifying the sky value, 
        the sigma of the sky value, and the number of elements used 
        to compute a sky value.   The 3 element form of SETSKYVAL
        is needed for accurate error budgeting.
PROMPTS
T_APER requires the number of photons per analog digital unit
(PHPADU), so that it can compute Poisson noise statistics to assign
photometry errors.    It first tries to find the PHPADU keyword in the
original image header, and if not found will look for the GAIN, 
CCDGAIN and finally ATODGAIN keywords.   If still not found, T_APER 
will prompt the user for this value.
PROCEDURES
APER, FTADDCOL, FTGET(), FTINFO, FTPUT, READFITS(), SXADDPAR, 
SXPAR(), WRITEFITS 
REVISON HISTORY
Written   W. Landsman   ST Systems Co.            May 1988
Store results as flux or magnitude                August 1988
Added SILENT keyword  W. Landsman                 Sep. 1991
Changed ERR SKY to ERR_SKY W. Landsman   March 1996
Replace TEXTOUT keyword with PRINT keyword  W. Landsman  May 1996
Check CCDGAIN or ATODGAIN keywords to find phpadu W. Landsman May 1997
Converted to IDL V5.0   W. Landsman   September 1997
Updated for new FTINFO calling sequence   W. Landsman  May 2000
Added /EXACT keyword                      W. Landsman  June 2000