How to Pre-process with no darks or bias?

[timc770]

Hello,

I have a DSLR image that I want process entirely in PI.  Although I normally shoot lights, darks, flats, and bias, I used in-camera noise reduction for this shot (sort of an experiment) and I took flats.  I am finding that the batch pre-processing script doesn't like this.  Is there a way to use the script with only lights and flats or must I take another approach?  If I can't use the script, some general guidance on what tools and process to use would be much appreciated!

Tim

[pfile]

i think the problem is that the flat scaling is wrong when there's no calibration of the flats. since the flats were probably not taken with in-camera noise reduction, you'll probably have to do the calibration of the lights manually. BPP will try to calibrate the flats and lights with any bias frames that you use, and since the lights were taken with ICNR, they are already bias (and dark) subtracted. so BPP will mess everything up.

what is the duration of the flats? if they are short enough you can just make some bias frames, then manually calibrate the flat subs with a master bias made from those bias subs. then you can try calibrating the lights only with the calibrated master flat and see what happens.

so: ImageIntegration on the bias subs (no scaling/weighting), save the integration as master bias, then ImageCalibration on the flat subs with only the master bias, then ImageIntegration of the calibrated flat subs (multiplicative normalization, weights either don't care or average signal strength), then save that integration as the master flat. finally IC on the lights, using only the calibrated master flat (make sure to leave "calibrate" unchecked), and then StarAlignment on the calibrated lights and finally ImageIntegration on the registered lights.

rob

rob

[timc770]

Rob - thanks very much for the suggestions.  The flats were taken with ICNR as well.  I think I will just wait until next target where I will shoot my usual darks and bias to try the pre-processing script with a DSLR image in PI (I have used it before successfully with mono ccd images).  I'll just stack in DSS and bring over to PI.  I've already done that once and wound up with a blotchy background somehow and was thinking maybe the DSS stacking was to blame in some way.  I'll take another crack at the processing in PI to try to control the blotchiness.

Tim

[pfile]

that's interesting. i didn't know the ICNR would fire on short exposures. anyway in theory because of this, both the flats and the lights are pre calibrated, so you might try just stacking the flats with II and then calibrating the lights with IC. maybe it would work. i think BPP wants bias/darks so it won't work with these frames.

rob