NAME

vigdata -- apply the vignetting corrections to an IRAF data (image) file

USAGE

vigdata image vignimage vigncorr back_frac

DESCRIPTION

This is a script task which builds a command string for the IMCALC task to perform a subtraction of vignetting effects from the input image. The image is multiplied by the vignetting correction file. If the image has not been background subtracted, then it is possible to specify a fraction of the total image counts to be background ("backfrac" ). The vignetting correction is then applied to the non-background counts in the image.

	vimage = (1.0-backfrac) * vigncorr * image + backfrac * image

PARAMETERS

image = prompt = input image file

The name of the input xray data file to which the corrections are to be applied.

vignimage = prompt = output vignetted image file

The name of the output xray image file which has been corrected for vignetting.

(errimage = ) [string]

The name of the input error file associated with the input image file. If NONE is entered, an output error array will not be created. If NULL or "." is used, the default error filename will be constructed.

(errvignimage = ) [string]

The name of the output error file which has had the vignetting applied to it. If NULL or "." is used, the default error filename will be constructed.

vigncorr = prompt = vignetting corrections mask

The name of the data file containing the vignetting corrections. This can be either an IRAF image ( -.imh ) or mask ( -.pl ) file.

back_frac = "0.00" prompt = fraction of image which is non-vign

			 bkgd (x.xx format)

The fraction of the counts which are not vignetted. The vignetting correction will only be applied to that fraction of the image which is vignetted.

(clobber = no) [boolean]

If this is set to yes, an previous version of the output file will be silently overwritten. A no will prevent an overwrite.

EXAMPLES

1. This will create the new image vi296.imh by applying the vignetting corrections from i296_vig.pl to 80% of the input data file, i296.imh. No error arrays will be generated.

vigdata

	Input image file: i296
	Output vignetted image file: vi296
	Vignetting corrections mask: i296_vig.pl
	fraction of image which is non-vign bkgd (x.xx format)  (0.20):
	Input error image (NONE): NONE

2. This will create the new image vi296.imh by applying the vignetting corrections from i296_vig.pl to 100% of the input data file, i296.imh. Error analysis will be done with the file i296_err to be produce vi296_err.

vigdata

	Input image file (i296): 
	Output vignetted image file (vi296): 
	Vignetting corrections mask (i296_vig.pl): 
	fraction of image which is non-vign bkgd (x.xx format)  (0.00):
	Input error image (NONE): .
	Output vignetted error file: .

TIME REQUIREMENTS

This operation takes ~30 seconds on a 256 x 256 data array.

BUGS

Since this is script task at present, it is a bit primitive. It does not check that the input data have already had a vignetting correction applied.

SEE ALSO

IMCALC and MAKEVIG