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#1 tloebl

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Posted 23 May 2020 - 03:10 PM

Hi,

 

the image is a calibrated image with only histogram transform over applied so it becomes visible. I am aware there is a bit of drift due to flexure. I can get rid of the smeary background but I wonder if someone can give me a clue as to what it might be caused by. I thought it might be an older dark frame with uneven hot/cold pixels causing it but I just tried a brand new series of darks and the problem is still there. Is there any parameter in light calibration or image integration in PI that could cause this pattern rather than a random background?

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  • integration.jpg


#2 tloebl

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Posted 23 May 2020 - 03:12 PM

Sorry for the double post...



#3 Tapio

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Posted 23 May 2020 - 03:12 PM

Looks like lack of dithering?

#4 Stelios

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Posted 23 May 2020 - 03:17 PM

Agree--looks like FPN (fixed pattern noise) which dithering removes. 


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#5 xiando

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Posted 23 May 2020 - 03:20 PM

 What they said above.

 

See 

 

https://www.cloudyni...-in-processing/

 

https://skyandtelesc...oduction-noise/

 

https://astrobackyar...trophotography/

 

https://skyandtelesc...r-astro-images/



#6 tloebl

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Posted 23 May 2020 - 03:28 PM

Thanks for the links. I am aware of dithering though I have never used it in 15 years of imaging. This issue only started recently. My stacked images in the past never showed this pattern. 


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#7 tloebl

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Posted 23 May 2020 - 04:36 PM

The attached is with a different camera, a 1600mm, using the same telescope/mount/tracking, etc., with similar processing and no dithering. I don't see the same effect. Does this happen sometimes, but not every time, w/o dithering?

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#8 xiando

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Posted 23 May 2020 - 05:43 PM

Thanks for the links. I am aware of dithering though I have never used it in 15 years of imaging. This issue only started recently. My stacked images in the past never showed this pattern. 

Understood. Just wanted to share them in case you "weren't aware and wanted to learn (I'm too lazy to write an article on it in a forum post... much lazier cough easier to drop a few links ;)

 

 

Best wishes.



#9 tloebl

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Posted 23 May 2020 - 06:12 PM

No problem, I appreciate any information...


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