Narrowband Calibration Problem

According to the FITS headers, some Ha frames were captured at EGAIN=1.00 e-/ADU (corresponding to a gain setting of 139 in the camera driver) and some at EGAIN=2.09 e-/ADU (corresponding to a gain setting of 75 in the camera driver), see appended Statistics.txt. The FITS header of the MasterBias, MasterDark and MasterFlat shows EGAIN=4.96 e-/ADU (corresponding to a gain setting of 0 in the camera driver). All other settings being equal, one would expect a lower median value in the MasterDark than in the Ha subframes. This is not the case, the median of the MasterDark is 1710 ADU, the medians of the Ha subframes are in the range of 1040 to 1152 ADU (this is the reason that the calibrated subframes are all black). So I conclude that the offset setting in the camera driver was differing as well between Ha subframes and calibration files.

The Ha subframes were captured with SGP. Which camera driver did you use for the Ha subframes (native or ASCOM)? Did you change gain and offset settings during the capture session?

Which capture software, which camera driver and which offset setting was used for the bias, dark and flat frames?

Can you please upload one dark frame that was used in the generation of the MasterDark?

Bernd
 

Attachments

  • Statistics.txt
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fredvanner said:
There doesn't appear to be anything wrong with the light subs, they just have a much lower bias (~900ADU) compared with the master bias (~1574ADU). Short of a change of gain setting, I can't think what could cause this.
Click to expand...
Hi Fred,
Thans for the info. I have revisited all my settings for capture and have found a couple of issues.
1. I appear to have changed (and this was not intentional) the Camera dirver from ZWO to Ascom. Dont know how I did this but have now changed it back.
2. Also changed the gain to 75 on one of the sessions (agian this was not intentional) have reset to 139 and saved all settings.

I will test this out on the next clear night and hope this fixes the problem. along with Bernds sugestions above.

I have put a couple of RAW Bias, Flat and Dark frames in the folder if you want to investigate any further.

I have never done Dark Flats, is this something I should be doing - maybe instead of Bias?
 
Phil Swift said:
Hi Fred,
Thans for the info. I have revisited all my settings for capture and have found a couple of issues.
1. I appear to have changed (and this was not intentional) the Camera dirver from ZWO to Ascom. Dont know how I did this but have now changed it back.
2. Also changed the gain to 75 on one of the sessions (agian this was not intentional) have reset to 139 and saved all settings.

I will test this out on the next clear night and hope this fixes the problem. along with Bernds sugestions above.

I have put a couple of RAW Bias, Flat and Dark frames in the folder if you want to investigate any further.

I have never done Dark Flats, is this something I should be doing - maybe instead of Bias?
Click to expand...
Sorry Fred, looks like I deleted the RAW files after I made the Masters.
 
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