CCDLIN-Applies a linearity correction to AAO CCD data

Description:

CCDLIN applies a linearity correction to AAO CCD data. The correction applied has the form determined by John Barton (RCA#5 Non-Linearity Correction - AAO internal document), and has two parameters: a correction factor (alpha), and a bias whose value is assumed when applying the correction.

Parameters:

IMAGE

The name of the image to be corrected for non-linearity. It should be a raw image obtained with an AAO CCD.

OUTPUT

Specifies the resulting corrected image. If this is the same as IMAGE, the image is corrected in situ. Otherwise, a new image is created.

ALPHA

The value of the correction factor used. The correction is given by

M=C*(1+alpha*C)

where M and C are the measured and corrected intensities (after bias subtraction) respectively. John Barton's memo gives a value of alpha=3.16E-6, and this is the reset value.

CBIAS

Since the linearity correction is expressed in terms of intensities after bias subtraction, a bias must be assumed during the calculation. The value is not very critical (any error in bias results in a much smaller error in the corrected data), and can safely be assumed to be constant over the image. The reset value is 180.

Source comments:

 C C D L I N

 Applies a linearity correction to data from the AAO RCA CCD.
 The correction applied is that given by John Barton (RCA#5
 Non-Linearity Correction, AAO Internal Document).

 Command parameters -

 IMAGE   (Character) The name of the structure containing the image.

 ALPHA   (Numeric) The value of the constant alpha in the expression
         giving the linearity correction.

 CBIAS   (Numeric) The value of the bias level to be applied when
         making the correction.  This is not a particularly critical
         parameter.

 OUTPUT  (Character) The name of the result of the operation.  This
         can be the same as for IMAGE.  If not, a new structure
         is created, with everything but the data a direct
         copy of the input.
                                  KS / AAO 10th Sept 1986