A PSF look-up table for Chandra ACIS-I data has been calculated and is available for download below. The PSF table is fully described in Laird et al. 2009 and we strongly advise you to read this paper and the README file accompanying the data before using the PSFs.

Briefly, using the MARX image simulator (Wise et al. 2003) elliptical PSFs have been calculated for four energies - 1.0, 2.5, 4.0 and 5.5 keV - over a fine, evenly spaced grid (10 pixel spacing) covering the ACIS-I detector. At each position and energy the ellipse parameters (semi-major axis, semi-minor axis and the ellipse angle) have been calculated for the 50, 60, 70, 80, 90 and 95% encircled energy fractions (EEFs). The positions in the PSF table refer to the Chandra ACIS-I detector coordinates ('detx' and 'dety').

A script to query the PSF table is also included in the download. For a given input energy band and position the script returns the PSF parameters (for all EEFs) for the nearest neighbour position in the PSF grid. The input position can be given in sky coordinates or RA and Dec if the corresponding Chandra image supplied, otherwise detector coordinates are required. Please see the README file provided with the release before using the script.

If you find these products useful for your research please acknowledge Laird et al. 2009.