Image Calibration

[cfranks]

Hi,
I have a problem associated with Drizzle processing that someone may have an explanation for, or a suggestion to help.  I am using a QSI540 which, as others have mentioned here, has defects called Hot Columns.  These are completely cleaned up with the standard Image Calibration except (for me) if the image has been dithered prior to Drizzle processing.  Obviously, Dithering should not change the location of the Hot Column , the same as it doesn't change the location of a Hot Pixel so I can't understand what might be happening.  I have uploaded the 2 raw and 2 calibrated files to Endor, together with the 3 Master files used, (cfranks folder), if anyone cares to look. The 2 images were calibrated at the same time with the same settings using either ImageCalibration or BatchPreProcessing. '0001' was not dithered, '0016' was.  They were taken 3 weeks apart which might be related but I don't know why.
Thanks,
Charles

[lucchett]

Hi, I am not sure I got it, but I think you should correct your defect before integration.

I do the same with dithering and a non linear column , that is not fully corrected after calibration.
dithering does change the position of a hot pixel, and for that reason you need to apply calibration first.
when you align the frames the "remnants" of not fully corrected hot pixels change their relative positions and then you reject them during integration

so:
-calibration
-cosmetic correction on the single frames
-alignment & integration

I do prefere to run the sequence manually, outside of BPP script


Ciao,
Andrea

[cfranks]

Thanks Andrea,  my 'problem' is just with calibration.  Images , same exposure, same object, seem to calibrate well when not dithered but calibrate badly when dithered.  I couldn't understand why.  I have now used somewhat successfully, the CosmeticCorrection Defect List with the prominent Hot Columns defined, to begin to tidy up the recalcitrant images.

Regards, Charles