iraf.net

NUMBER:	253
MODULE:	transform, apall, apsum
SYSTEM:	V2.9
DATE:	Mon Jul 25 14:14:57 MST 1994
FROM:	valdes

BUG:	The extraction of dispersion calibrated long slit data, the
	result of TRANSFORM, does not properly pass on the dispersion
	information.  One symptom of this is that if the dispersion axis is
	2 then the final extracted spectrum will have a wavelength per
	pixel corresponding to the first axis in the CD1_1 keyword.  Note
	that there is also a correct WPC and CDELT1 keyword.  This does not
	cause a problem when using V2.9 ONEDSPEC routines because WPC has
	precedence over CD1_1.  However in taking this data to V2.10 the
	precedence was changed and CD1_1 is used in preference to WPC or
	CDELT1.  So a task like V2.10 SPLOT will plot the spectra with an
	incorrect dispersion.  The work around to update the header for
	V2.10 is update the CD1_1 keywords or delete them:

	    cl> hedit <1D spectra> cd1_1 '(wpc)'
	    cl> hedit <1D spectra> cd1_1 del+

STATUS:	The aperture extraction in V2.10 correctly passes on the
	dispersion coordinates produced by TRANSFORM during the
	long slit reductions.