Over-calibration with flats?

[kwood]

I am getting a strange result when using WBPP. It seems to be over-reducing the flat from the raw data. I am using a new QHY600M (0 gain, 40 offset, Mode3). All luminance, darks, flats and bias were taken with same settings and temperature. I am getting the same result with luminance and all color data as well. I have tried changing the ADU setting for the flats, with no appreciable difference. I have tried taking the flats with different gain settings, but that didn't seem to make a difference. I have tried different settings within WBPP. (Calibrations settings for Dark and Flat have been set at "Auto", as well as "600s". I have used "Optimize Master Dark" and also left it unselected, with now appreciable difference.)

Here is a link to the luminance data. Raw subs for the Lum and flats and masters for darks and bias. All taken at -15 degrees, 2x2 with same camera settings. https://www.dropbox.com/sh/uhqcb263fzkmjdv/AACGMK4yATKon7SUn3_lCL_La?dl=0

I am also attaching JPEG's of a single lum subframe, the flat master and luminance master after WBPP processing.

Thank you in advance for taking some time to help me. I have reviewed the responses to the recent post on a similar issue, but was unable to find a solution there.

Thanks,
Kent

 

[pfile]

do you have darks that match the duration of the flats? you can probably get away with calibrating the flats with bias frames only; did you try that?

rob

 

[bulrichl]

Your MasterDark (600 s) has a median value of 695, the MasterBias has 2598. This is impossible when the same gain and offset was applied.

Bernd

 

[kwood]

Hi Rob, thanks for the quick reply. Yes, I did try using 2s darks for my flats, but it didn't seem to make difference. I have added that folder to the folder linked above. I just finished trying calibrating the flats with bias only and am attacking the JPEG of Masterlum. Didn't seem to make a difference. Also attaching a screen shot of the WBPP settings used for that bias run.

Thanks,
Kent

 

[pfile]

per bernd's reply it sounds like your calibration frames don't match each other... you might want to check that. make sure to use the same capture software, driver version and driver type for all of your frames.

 

[kwood]

Your MasterDark (600 s) has a median value of 695, the MasterBias has 2598. This is impossible when the same gain and offset was applied.

Bernd

Bernd, thank you. You are absolutely right. I am a bit perplexed regarding how this occurred, but when I went back and looked at the individual files, the gain was set to 26 and offset to 10 for the darks. Not sure how that happened... I will take some new darks.

Thank you all for your quick and insightful responses!

I imagine this will resolve the issue and I will confirm once complete.

Thank you!!
Kent