Parameters for "findstars"

Start by opening a DS9 window before running this task and by editing the parameters for the task "findstars".
The task parameters will look like this:





This task will search for field stars in a specified image and make
a list of such stars with their pixel coordinates. This task is used to
find reference stars in a template galaxy image.

Start by specifying the name of the SN+galaxy image in the "image" parameter.

The "opt_ir" parameter specifies whether you are working with CCD or infrared images.

The "coordinates" parameters is the name of a text file where the (x,y) coordinates
of the selected stars will be stored.

The CCD parameters "scale", "datamin", "datamax", and "epadu" are self explanatory.

The "fwhmpsf" is a parameter that specifies the FWHM of the PSF in arcsec
and is used to automatically find field stars. The parameter "threshold" is
in units of the FWHM of the sky brightness distribution, and defines the
threshold to begin star detection in the image, and "nstars" sets
the minimum number of stars to find in the input image.

The "cbox" parameter specifies the centering box in arcsec.

The "wcsout" parameter determines the output coordinate system and
must be set to "physical".

Running the task "findstars"

The task will start by searching for the brightest field stars in
the specified image (B.final, in this example). The "threshold"
parameter will be used to identify the brightest stars. If the task
doesn't find "nfind" stars, it will divide the threshold by two,
and continue with the search until it finds "nstars" stars.

The output of this task is a two-column text file with the pixel
coordinates of the selected stars (B.final.coo in this example).