BatchPreprocessing script and Dark Flats instead of Bias

[mexbound]

I have been using the BatchPreprocessing script successfully with my QHY8L CCD camera. I have a new CMOS camera (ZWO1600MC-Pro) and have been reading about using Dark Flats instead of Bias frames.  When using the BatchPreprocessing script how would I apply Dark Flats instead of Bias?  Would I just add the Dark Flat frames to the Bias tab of the script?

[RickS]

Just do a separate run of BPP to create the master flat with the Dark Flats loaded as Darks.  Then use the master flats in your normal processing.

[mexbound]

Just to verify I have this correct. I have the following files:

Lights
Flats
Darks
Dark Flats

I do a separate run of BPP to create a "Master Dark Flat" using my Dark Flats loaded as Darks.

So in my second run of BPP I load my "Lights" on the Light Tab, my "Flats" on the Flats Tab and my "Darks" on the Dark Tab.  I then load my "Master Dark Flat" as the first file under the Flats Tab and check mark the "Use Master Flat" check box. Nothing goes into the "Bias" tab.

Do I have this correct?   And thanks for your help on this.

[RickS]

1. Run BPP with dark flats (loaded as darks) and flats (loaded as flats) to produce a master flat.
2. Run BPP with darks, master flat and lights.

Cheers,
Rick.

[mexbound]

Thanks RickS!    I got it now.

[juliangeorgeshaw]

So if I have dark flats with different exposure times I must run BPP as outlined above for each of them separately?
So for LRGB run BPP 8 times all together? 

(I have dark flats for LRGB with exposure times of 1.5, 2.5, 3 and 5 seconds respectively. I was hoping that if I load all my dark flats at once that BPP would make 4 different master flats in one run. But unfortunately when I load all the dark flats BPP describes them all as "1.5 sec" and makes one master flat out of all of them  .

Interestingly, if I add 120 sec Darks (which matches the exposure of all my lights) using "Add Darks" then BPP does see a difference between them and the dark flats; it describes the 120 sec darks as "120 sec". However simultaneously it still describes ALL the short exposure dark flats, regardless of their actual exposures, as "1.5 sec".
)

Julian   

[juliangeorgeshaw]

I just read this on Dave Ault's "Trapped Photons" blog:
If your dark exposures are all within 10 seconds they will all get lumped into the same stack.

I changed my exposure tolerance from 10 to zero (only integer values of tolerance seem to be allowed) and now my Dark Flats are in different stacks according to exposure time.

Thank you Dave.