iraf.net

NUMBER:	226
MODULE:	artdata.mkobjects
SYSTEM:	V2.9-V2.10.2
DATE:	Fri Sep 17 14:13:24 MST 1993
FROM:	valdes

BUG:	The scales of the 'expdisk' and 'devauc' images are incorrect due
	to an integer truncation error.  The error is such that the actual
	output radius for a given input radius is given by the formulas:

	expdisk:  rout = rin * int(ln(D)/1.6783) / ln(D)/1.6783
	devauc:   rout = rin * int(ln(D)/7.67)**4) / (ln(D)/7.67)**4

	where D is the dynamic range parameter in the ARTDATA package
	parameters, ln() is the natural logarithm, int() is the integer
	truncation function, and ** is the exponentiation operator.
	From this one can, fudge the input radii to give the
	desired output radii, select a dynamic range where the correction
	factor is 1, or account for this as needed when the artificial
	image is analyzed.  The simplest thing is to adjust the dynamic
	range; for example, a dynamic range of 126514 for the 'expdisk'
	model is the closest to the default value of 10000 which will give
	correct output scales.

STATUS:	Fixed in V2.10.3

NUMBER:	514
MODULE:	sensfunc
SYSTEM:	All
DATE:	Fri Nov 22 11:56:05 MST 2002
FROM:	valdes

BUG:	This report is not actually a bug but a guide as to the source of
	the error 'no degrees of freedom' from the task SENSFUNC.  If the
	standard star file used with the task STANDARD has the standard
	values in flux units instead of magnitudes there will be no
	apparent error from that task.  But the file produced will have
	zero or very small numbers for the points to be fit by SENSFUNC.
	Using this file with SENSFUNC produces the error 'no degrees of
	freedom'.  So if you see this error and it is not solved by using
	lower fitting orders then it is probably the values in the file
	produced by STANDARD were generated from an incorrect standard data
	file given in flux.

	Why this has come up is that if you retrieve standard star data
	from the ESO web pages be sure to get ones given in magnitudes
	and not in flux.

STATUS:	No change is contemplated at this time.