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  Monday, 03 October 2022
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Hi folks,

 

I am experiencing some issues with my Pier 5 datasets and hope you have a solution for that ;-)

After the stacking process one of my first steps is the background extraction to remove the slight vignetting wihich is still left in the images.

No matter what tool (PixInsight, AffinityPhoto) or method (DBE, ABE, manually) I use, I always have those large ring artefacts afterwards. This is kind of annoying and takes me forever to manually remove. I am not having such issues with Pier 1 data for instance.

I am pretty sure I use the correct Dark and Flat files from the time the images were recorded.

The ring artefacts exists in almost every dataset I worked on lately, so this is just one example but looks pretty much the same on other images as well.

Any ideas? Do you face the same problems? How do you solve it?

 

Best regards,

Martin

1 month ago
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#5525
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Thanks for your advice - I will try to re-stack with your suggested correction pathways and hope the result will be much better. I´ll let you know, might take me a few days thogh.

Thx!

2 months ago
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#5523
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Hi Martin,

Hopefully the suggestions have cured the problem for you and we will soon get to see the result.

If for any reason it doesn't then when using WBPP and before selecting to run it, is their a note saying that "No Master Flat will be used to calibrate the frames." I very much doubt it as I am sure you would have rectified the issue, however, the result you show can be closely replicated if a flat is not being used. Very strange. 

Cheers, 

Ray 

2 months ago
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#5521
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Hi Martin,

As old_eyes says something is not right with your flats calibration. I use WBPP in Pixinsight and haven't had any issues. WBPP calibrates the flats with the master bias, and then the lights with the master flat and master dark.

Chris

That’s exactly the method I use, although I don’t use WBPP to create master calibration files (it just adds processing time as we don’t do nightly flats).

A lot of older books and online tutorials do not use the right methods for CMOS cameras.

2 months ago
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#5519
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Hi Martin,

As old_eyes says something is not right with your flats calibration. I use WBPP in Pixinsight and haven't had any issues. WBPP calibrates the flats with the master bias, and then the lights with the master flat and master dark.

Chris

2 months ago
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#5516
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The Master Flat is over/under compensating. I had similar problems a while ago.

I found this advice on the Pixinsight forum from the Pixinsight team:

"Dark frame optimization is not recommended for cameras with a CMOS sensor. Presumably the preparation of the MasterFlat is causing the issue. Please calibrate the flat frames with the MasterBias only, then integrate the calibrated flat frames to the MasterFlat."
 
Since only calibrating the flats with the Master Bias I have had no problems (see my SH2-155 uploaded today in this topic. There are many things that could be improved in this image, but at least it does not show the ring effect).
 
Not guaranteeing it will work for you, but it is worth a try to eliminate one obvious potential issue if you are calibrating flats with darks.
 
old_eyes
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