An array CPV is used to store all data points according to different pixels and chopper positions. Now these vignetting factors for each pixel are displayed along with their polynomial fits. After each pixel display, the user is asked to select which fit to use for correction. Please refer to the following setup for the pixel arrangement on the IDL display window. If no, the vignetting correction is skipped.
C Uses a moving median method to calculate the average drift of each pixel.
The value should not be too small. To understand how a moving median is computed in the program, follow the example given below. Again, for the 152th point, it is the median of all points between the second and the 301th point. This continues similarly till the 300th point. Hence, the pattern of grouping the data points for the median is done symmetrically around the mid-point.