iraf.net

NUMBER:	412
MODULE:	imcombine
SYSTEM:	V2.11
DATE:	Tue Oct 13 11:16:46 MST 1998
FROM:	valdes

BUG:	Updating of the image coordinate system when combining offset images
	is not being done correctly.  The effect is that the header of the
	combined image corresponds to the first image.  One workaround is
	to look at the offsets printed by IMCOMBINE.  Then redo the
	combining putting the image which shows offsets of (0,0) (if there
	is one) as the first in the list to combine.  A more general
	workaround is to look at the first image listed and get the offsets
	(for example (220,50)) and use these to update the header.  To
	update the header using the offsets printed for the first image

	cl> hedit outimage crpix1 '(crpix1+220)'
	cl> hedit outimage crpix2 '(crpix2+50)'

	where 220 and 50 would be replaced by the offsets from the IMCOMBINE
	listing.  This will fix the work coordinate system.  If the
	physical coordinate system also needs to be correct do the
	same with the keywords LTV1 and LTV2 replacing CRPIX1 and CRPIX2.
	Note that this extends to higher dimensions if combining images
	with more than 2 dimensions.

STATUS:	Fixed for the next release.