I've found a few threads that loosely indicate what I think I've found. This thread is in part for ease of future discovery by others, and in part for my own knowledge. If others would please confirm what I'm seeing it would be greatly appreciated.
Regarding BPP - it seems that it expects a non-calibrated master dark (i.e. not bias subtracted).
I've been manually preprocessing my data for a while. I have a master library that I reference frequently. For the first time in a while I ran BPP. I fed it my master frames and lights and let it rip. The result was I suppose you might call an overapplicaton of the flat master to the lights. That is - my master flat (which was created by BPP in the first place) grossly overcorrected the light frames. I ran through the process manually using the BPP generated master flat - no overcorrection.
I was able to reproduce the overcorrection by checking the "calibrate" box for the master dark in ImageCalibration. I also found BPP outputs the following further confirming what I'm seeing:
The result of subtracting bias twice from the master dark seems to push the flats to overcorrect.
So it seems that if you wish to use your master frame library for both BPP and manual preprocessing you should at the very least not calibrate your master darks. I see no log indication of similar behavior of BPP with master flats so I'm not sure if it's doing the same to those. Anyone know?
Regarding BPP - it seems that it expects a non-calibrated master dark (i.e. not bias subtracted).
I've been manually preprocessing my data for a while. I have a master library that I reference frequently. For the first time in a while I ran BPP. I fed it my master frames and lights and let it rip. The result was I suppose you might call an overapplicaton of the flat master to the lights. That is - my master flat (which was created by BPP in the first place) grossly overcorrected the light frames. I ran through the process manually using the BPP generated master flat - no overcorrection.
I was able to reproduce the overcorrection by checking the "calibrate" box for the master dark in ImageCalibration. I also found BPP outputs the following further confirming what I'm seeing:
Code:
Applying bias correction: master dark frame ...
The result of subtracting bias twice from the master dark seems to push the flats to overcorrect.
So it seems that if you wish to use your master frame library for both BPP and manual preprocessing you should at the very least not calibrate your master darks. I see no log indication of similar behavior of BPP with master flats so I'm not sure if it's doing the same to those. Anyone know?