iraf.net

NUMBER:	214
MODULE:	scopy, sarith
SYSTEM:	V2.10-V2.10.2
DATE:	Thu May 20 17:07:53 MST 1993
FROM:	valdes

BUG:	When using SCOPY or SARITH with a specified wavelength range,
	w1 and w2 not equal to INDEF, and rebin=yes the spectra are
	correctly resampled to the requested wavelength interval but
	the coordinate system in the header is updated incorrectly.
	The coordinates may be off by a fraction of a pixel.  For
	example if w1=6400 and w2=6600 the output data will have
	the first pixel at 6400 but the coordinate reported by
	LISPIXEL or any other task might be 6400.25 (where the
	dispersion is, say, 3 Angstroms per pixel).  This error
	is caused during the conversion from logical to physical
	pixel coordinates when the physical coordinates are treated
	as integer; i.e. a wavelength of 6400 for the first logical
	pixel might be physical pixel 185.325 but it is then
	truncated to 185 and the coordinate system is set so
	that physical pixel 185 is 6400 and pixel 185.325 is
	6400.25.  This is a subtle error which may be discovered
	by looking at the coordinate of the first pixel with LISTPIX
	and comparing it with the requested wavelength of the first pixel.

STATUS:	Fixed in V2.10.3.

NUMBER:	251
MODULE:	sarith, scopy
SYSTEM:	V2.10.0 - V2.10.2
DATE:	Wed Jun 29 17:32:20 MST 1994
FROM:	valdes

BUG:	For multispec spectra which have a doppler factor in the coordinate
	system description (a non-zero value for the 7th field following
	the number of pixels) making a copy or doing arithmetic will
	cause the wavelength zero point to be off by a factor of
	1/(1-z*z).  The workarounds are to either avoid introducing
	a doppler factor, accounting for the error, or explicitly
	setting w1,w2 (but note bug #214).

STATUS:	Fixed 10/92 and included in V2.11.