Calibration wasn't ...
 
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Calibration wasn't working correctly - Solved myself - Gain and offset were different for Calibration frames

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(@rms401)
White Dwarf
Joined: 4 years ago
Posts: 6
Topic starter  

I have one of the new ASI6200mm cameras. I gathered a bunch of darks and bias when I first got it. Later, I changed the gain and offset to experiment with read noise, well depth and offset amount. I was reusing the darks and bias while gathering new flats for test images. All of a sudden I could not get my flats to remove dust donuts and calibration was really causing strange "bright" vignetting. I tried changing APP setting and calibration was still not working. Then I realized I had changed gain and offset from the initial darks and bias. I redid my darks and bias with the new gain and offset. Now APP works great again. 

 


   
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(@vincent-mod)
Universe Admin
Joined: 6 years ago
Posts: 5386
 

Thanks for explaining your workflow and solution! Yes indeed, changing the gain will change the noise profile which causes a mismatch for calibrating the flats.


   
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(@rms401)
White Dwarf
Joined: 4 years ago
Posts: 6
Topic starter  

I am not so sure that the gain and offset were my calibration problem. Did that make sense, Vince?

I had the same problem again even with the correct gain/offset for lights and calibration frames. I was also getting an error about "Corrupted Image" randomly on all types of files. Then I noticed that there were both upper and lowercase filter names. My setup uses filter names that are all lower case - lum, red, green, blue etc. The load dialog shows my lower case names along with Luminance, Red, Green....etc

Once I assigned my frames to the correct filter name (my name variations were listed at the top of the channel assignments), calibration worked fine. I also no longer got the "Corrupted image" errors.

I will rename my filters in my capture software (SKYX) to match APP names. That should keep me from making the wrong assignments. Maybe APP should check for name variations to prevent this? I'm sure others have made the same mistake without even realizing it. 

Randall

PS - using the image viewer and switching between linear/l-calibrated makes checking the calibration results easy. Best to check this before continuing in case calibration didn't work well. That is really a great feature of APP.

This post was modified 3 years ago 2 times by rms401

   
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