psf - estimate the point spread function

  psf[/qualifiers]

Calculates differential and integral Point Spread Function and plots them onto the currently defined graphic device. The expected PSF for a pointlike source is also calculated and displayed. This command needs an accurate estimate of the image background. Use the command back/opt before running psf.

The default counts all the events within an annulus that increases by one pixel per iteration. Use the /box qualifier to use boxes instead.

psf/back=x

Enter the image background in units of cts/original-pixel. This can be obtained using the BACK/OPT command.

psf/box

Use boxes, not annuli.

psf/calfile

Write the psf to an ascii file called ximage_psf.dat, which can then be picked up by detect, sosta, etc....

psf/cursor

Enter the position of the centroid and outer radius using the cursor.

psf/energy

The expected PSFs for different detectors are derived in XIMAGE using the 'theoretical' algorithms usually derived from ground or inflight calibration data. Dependent on the detector the expected PSF can be energy dependent. This qualifier allows to specify the 'interesting' energy value (in keV, the default value is 1.0). The expected PSF is plotted together the measured PSF.

psf/x=n

Specify the x coordinate n for the center of the box position.

psf/y=m

Specify the y coordinate m for the center of the box position.

psf/fileout=name

Write the psf results to an ASCII file called name.

psf/print

Write on the terminal the quantities calculated for each step.

psf/radius

Give the outer radius in arc minutes.

Examples:

psf/cur/back=2.3e-03         ! calculate the psf for a position specified
                             ! by the cursor and setting the background.
psf/cur/back=2.3e-03/rad=6   ! calculate the psf for a 6 arc min rad