scaled PSF
substar image photfile exfile psfimage subimage
image
The list of images from which to subtract the scaled and shifted PSF.
photfile
The list of photometry files, or directory, containing the input photometry.
If photfile is "default", "dir$default", or a directory specification,
SUBSTAR will look for a file called image.nst.? where the question
mark stands for the highest existing version number.
Otherwise photfile must specify one photometry file for each
image in image.
Photfile is usually the output of the NSTAR task but may also
be the output of the PEAK and ALLSTAR tasks or even the PHOT task.
Photfile may be an APPHOT/DAOPHOT text database or an STSDAS table.
exfile
The list of photometry files containing the ids of stars to be excluded
from the subtraction process. If exfile is "default", "dir$default",
or a directory specification, SUBSTAR will look for a file called
image.pst.? where the ? mark stands for the highest existing version
number.
Otherwise exfile must specify one exclude file for each
image in image.
Exfile is usually the output of the PSTSELECT task but may also
be the output of the PEAK, NSTAR and ALLSTAR tasks or even the PHOT task.
Exfile may be an APPHOT/DAOPHOT text database or an STSDAS table.
psfimage
The list of images, or the directory, containing the PSF computed by the
PSF task.
If psfimage is "default", "dir$default", or a directory specification,
then SUBSTAR will
look for an image called image.psf.? where the question mark stands
for the highest existing version number. Otherwise psfimage must
specify one PSF image for each image in image.
subimage
The list of output images, or directory where the output subtracted images are
written.
If subimage is "default", "dir$default", or a directory specification,
then SUBSTAR will write an image called image.sub.? where question mark
stands for the next available version number. Otherwise subimage
must specify one output image for every input image.
datapars =
The name of the file containing the DAOPHOT data dependent parameters.
If datapars is null ("") then the default file in the user's
uparm directory is used.
daopars =
The name of the file containing the DAOPHOT fitting parameters.
if daopars is null ("") then the default file in the user's
uparm directory is used.
verbose = )_.verbose
Print messages about the progress of the task? Verbose
verify = )_.verify
Verify critical SUBSTAR task algorithm parameters before task execution?
update = )_update
Update critical SUBSTAR task algorithm parameters if verify is "yes"?
SUBSTAR task takes an input photometry list photfile containing the fitted coordinates and magnitudes, and an input PSF psfimage, and for each star in the photometry list scales and shifts the PSF and subtracts it from the input image image. The final subtracted image is saved in the output image subimage.
The input photometry list can be the output from of the PEAK, NSTAR or ALLSTAR tasks or even the PHOT task although most people would not want to use the PHOT output for this purpose.
Selected stars may be ommitted from the subtraction by supplying their ids in the file exfile. Exfile is normally the output the PSTSELECT task and is used to tell SUBSTAR to subtract the PSF star neighbours, but not the PSF stars themselves.
The SUBSTAR task is most commonly used to check on the quality of the PSF fitting produced by PEAK and NSTAR, to search for non-stellar objects and close binary stars, to generate an improved PSF in crowded fields, and to remove neighbours from bright stars which are to be used to determine aperture corrections.
1. Subtract the NSTAR photometry results in the file n4147.nst.1 from the image n4147 using the PSF stored in image n4147.psf.1. The subtracted image will be named n4147.sub.1.
da> substar n4147 n4147.nst.1 "" n4147.psf.1 default verb+ verify+
2. Rerun the example above, submitting the task to the background and saving all the verbose results in a file called nstar.out. Remember to turn off the verify switch.
da> substar n4147 n4147.nst.1 "" n4147.psf.1 default verb+ verify- > nstar.out &