.help darksub Apr86 noao.imred.generic
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NAME
darksub -- Scale and subtract a dark count image
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USAGE	
darksub input output darkimage
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PARAMETERS
.ls input
List of input images from which to subtract the dark count image.
.le
.ls output
List of output dark count subtracted images.  The output images may
be the same as the input images.  The input and output image lists should
contain the same number of images.
.le
.ls darkimage
Dark count image to be scaled and subtracted from the input images.
.le
.ls exposure = ""
Header parameter name from which to obtain the exposure times.
.le
.ls pixtype = "1"
The pixel datatype of the dark subtracted images.  The default ("1")
is the pixel datatype of the original image.  The other choices are
"short", "integer", "long", "real", and "double".
.le
.ls verbose = yes
Print log of operations performed.
.le
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DESCRIPTION
The dark count image is scaled by the ratio of the input image exposure to the
dark count image exposure and subtracted from each of the input images.
The exposures are obtained from the image headers under the specified
name.  The output images may have the same names as the input images.
A temporary image is used for the scaled dark count image and the original
image is not modified.  The pixel datatype of the output images is
specified by the parameter \fIpixtype\fR.  The default ("1") uses the
datatype of the input image.  A log of the operations performed may be
printed on the standard output when the verbose options is specified.

Note that this task can be used to subtract any type of image from a set
of images in which the subtracted image must be scaled to a given exposure.
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EXAMPLES
To subtract the dark count image 'dark' from obs1, obs2, and obs3:

.nf
	cl> darksub obs1,obs2 obs1,obs2 dark exp="exposure"
	Tue 18:50:56 08-Apr-86
	  obs1 = obs1 - 5.0049997336067 * dark
	Tue 18:51:05 08-Apr-86
	  obs2 = obs2 - 5.009999733075 * dark
.fi
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SEE ALSO
imarith
.endhelp