Combining Flat Fields

In combining the flat field frames the filter type is of importance. Hence, the combining command will check for consistency of the keyword containing the filter type. The combining input parameters can be set up in the flat parameter table, similar to the dark frames. Table 3.6 show the default keyword settings.

 

Table 3.6: Keywords for combining flat field calibration frames

Keyword	Content	Default	Description
CCD_IN	input name	?	table of input frames
FF_TYP	descriptor value	*	exposure type to check, if any
FF_SIG	yes|no	no	create sigma image
FF_MET	comb. method	avsigcl	type of combining operation
FF_DEL	yes|no	no	delete cal. frames afterwards
FF_STA	mean|median|mode	mode	correct. by Mode/Median/Mean
FF_EXP	yes|no	yes	scale by exposure time
FF_SCA	yes|no	no	scale by MMM
FF_OFF	yes|no	no	add offset obtained from MMM
FF_WEI	yes|no	yes	use a weighted average
FF_SEC	area	[<,<:>,>]	area for computing MMM
FF_RAN	real,real	-99999,99999	valid pixel range
FF_CLP	real	3.,3.	low/high sigma clipping factor
FF_NUL	real	NULL(2)	value for rejections