id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc
1506	negative window found  in psphotStack  psf matching	bills	bills	"We are getting a number of staicsky failures where the psf matching fails due to a negative kron radius calculation. See log excerpt below.

The images don't look particularly bad.
Recent examples are sky_id 193594 and 193468

      Filtered out 58 of 538 sources
    built background image: 2.496715 sec
      image sky : mean -5.720879, stdev 296.211211, dQ 0.561366
      background sky : min -31.189825 mean -5.720878 max 16.422895 stdev 8.532555
        Iso-kernel region: [21:6285,21:6267] out of 6307,6289
      Found 29 stamps
        Kron Radii vs FWHMs 1: fwhm: 6.000000, kron 3.414591
        Kron Radii vs FWHMs 2: fwhm: 7.308946, kron -3.452876
        Windows from Kron Radii: 9.390125 for 1, -9.495409 for 2
Error in the psphot image loop

 -> pmSubtractionStampsGetWindow (pmSubtractionStamps.c:945): Unable to select stamps for PSF-matching
     Unable to determine normalisation window size (2).
 -> pmSubtractionMatch (pmSubtractionMatch.c:710): Unable to select stamps for PSF-matching
     Unable to get stamp window.
 -> matchKernel (psphotStackMatchPSFsUtils.c:303): Unable to select stamps for PSF-matching
"	defect	new	normal		psphot		normal