WBBP Challenge No Master Dark can be used so using bias -- WBPP 2.1.2

[gbarr56]

I retook all my calibration files last night....bias, darks, and flats with the different filters with the proper exposure. I am getting the message that No Master Dark will be used to calibrate the frames, the master bias will be used instead. This happens when I hit RUN.

Why won't my darks be used? I am having calibration issues in my master lights and think this may be my problem. See screen captures.

I have a monochrome camera.

Thanks for any help anyone can give me.

 

[robyx]

Hi @gbarr56,

this regards the flat frames only. Indeed, when WBPP calibrated the flat frames it looks for an exact matching master dark, if that master dark is not provided (as per your case, you don't have a master dark with the same exposure of your flat frames) and WBPP finds a master bias with the matching binning then it makes the choice to ignore the unmatching master darks and use the bias only.

Looking at your configuration, that's the correct choice since your master dark has an exposure of 600 sec which produces a dark uncorrelated to the flat frames, using it to calibrate your flat frames is to be absolutely avoided.

Hope it makes sense!!
Robyx

 

[gbarr56]

Hi Rob,
Thanks so much for getting back to me. Where do you see my master dark has a 600 second exposure? I only have 300 seconds (maybe typo) added. Not sure I'm following this.

Is there any benefit to me providing a flat frame exposure for a dark frame? Are you saying that if I had dark frames with all the flat frame exposure times, then I would not get this error? From Adam Block's video's, I saw that Bias=Dark if short exposure times <1-2min so my guess is NO. I just want to make sure I'm understanding you correctly.

 

[robyx]

Hi Rob,
Thanks so much for getting back to me. Where do you see my master dark has a 600 second exposure? I only have 300 seconds (maybe typo) added. Not sure I'm following this.

ops sorry my fault, it's 300s! I'm probably too used to see my 600s darks

Is there any benefit to me providing a flat frame exposure for a dark frame? Are you saying that if I had dark frames with all the flat frame exposure times, then I would not get this error? From Adam Block's video's, I saw that Bias=Dark if short exposure times <1-2min so my guess is NO. I just want to make sure I'm understanding you correctly.

the comparison between providing bias only or dark flat frames with the exact matching exposure is something that should be done case by case. The potential issue is due to a non-linearity that could exist on some cameras such that the behaviour at 0.5sec could be very different with respect to the behaviour at 2sec exposure. On other cameras, a bias of 0.01 sec is could contain the same data as a dark flat of 2 seconds.

Adam says that taking dark flats is always correct, using bias frames is probably correct except in some cases depending on the hardware.

So my suggestion is simply to use dark flats unless you're really sure that your bias frames correctly calibrate your flat frames.

Robyx

 

[gbarr56]

Rob,
Thanks. So I should just take dark frames with all the exposure times used for my flats for the various filters. Is that correct?

 

[robyx]

Rob,
Thanks. So I should just take dark frames with all the exposure times used for my flats for the various filters. Is that correct?

yes. After that, you can run a session where you don't add the dark flats but you add only the master bias and the master dark of 300s. By comparing the result in the two cases you should answer the question if it's worth taking dark flats or if it's enough to use a single master bias to calibrate all flats.

Robyx