Noisy Rosette Nebula despite 4 hours of data, Canon DSLR - pasted light subframes, see what you can do with them

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Karol Łoziński avatar

Hi, I’m having a hard time with material I gathered. Last night I took pictures of Rosette Nebula (NGC 2238), around 4h of data with the Canon DSLR EOS 7000D unmodified. While imaging, I was fairly sure that this amount of data will be sufficient to minimize noise. Temperatures were also on the low side - ranging from -2 down to -12 degrees Celcius. All of that and… it’s still painfully noisy, which is especially visible in starless image.

Underneath I’ve pasted a link to my images. Not a stack but all separate, light frames. Try your best, see what you can do with it and please help me answer some questions - am I doing someting wrong doing imaging? Am I doing something wrong in postproduction? Or is it high time to change the ‘ol DLSR for a dedicated astronomy camera.

https://mega.nz/file/mt4yiA5Y#eBxOjUB5URK1ZXr0Cpq7iYx3yoGmdR7W9Ix81Y0dFZs → All light frames (both CR2 and converted FITS)

https://mega.nz/file/zxInBArZ#qpu3miPif-id3FlYxecDw02sZywVakVuR9pxX4NM7JI → 60 mb PNG of best I could do. I’m aware of the blimp/ artifact.

Tony Gondola avatar

I stacked them and didn’t find the result to be unusually noisy. Unfortunately, the noise you do have is walking noise. Did you dither?

Karol Łoziński avatar

Usually, but not this time :( Did you have results similar to mine? Can you show your picture? Even a screenshot. And what software did you use?

Tony Gondola avatar

Here a stretched close crop to show what I’m talking about:

📷 2026-01-18T16.28.58.png2026-01-18T16.28.58.pngNotice how the noise shows a fine vertical lines, that’s walking noise. It’s what happens if you don’t dither. The only way to eliminate it without dithering is to have perfect PA so that any image movement frame to frame is random. Obviously, dithering is a lot easier.

Karol Łoziński avatar

Yeah I’ve noticed it, but it appears only while stacking in ASTAP. When I stacked in DSS (dithering turned off) it virtually disappeared.

Tony Gondola avatar

I stacked your frames in Siril and applied a simple histogram stretch, the walking noise is certainly there.

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Karol Łoziński avatar

Ok, thank you for your time and for checking!

So you think that dithering should help to reduce noise overall? Or will it just help with walking noise while the rest looks ok-ish and should be delt with in post-pro?

Tony Gondola avatar

Yes, I don’t think you have more noise than I would expect from an uncooled DSLR. I will mention that I just ran the full image through GraxPert and it cleaned up nicely so you might try that.

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Karol Łoziński avatar

I did and it was… ok. Good looking at first but it there was still a lot of noise to deal with later in post-production. But I guess I can’t expect miracles while working with material from such camera. I will try again but with dithering. Hope this will help clear some things out :)

Thank you very, very much for all your help and time!

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Tony Gondola avatar

Have fun!

kgav8r avatar

Karol Łoziński · Jan 18, 2026, 12:40 PM

Hi, I’m having a hard time with material I gathered. Last night I took pictures of Rosette Nebula (NGC 2238), around 4h of data with the Canon DSLR EOS 7000D unmodified. While imaging, I was fairly sure that this amount of data will be sufficient to minimize noise. Temperatures were also on the low side - ranging from -2 down to -12 degrees Celcius. All of that and… it’s still painfully noisy, which is especially visible in starless image.

Underneath I’ve pasted a link to my images. Not a stack but all separate, light frames. Try your best, see what you can do with it and please help me answer some questions - am I doing someting wrong doing imaging? Am I doing something wrong in postproduction? Or is it high time to change the ‘ol DLSR for a dedicated astronomy camera.

https://mega.nz/file/mt4yiA5Y#eBxOjUB5URK1ZXr0Cpq7iYx3yoGmdR7W9Ix81Y0dFZs → All light frames (both CR2 and converted FITS)

https://mega.nz/file/zxInBArZ#qpu3miPif-id3FlYxecDw02sZywVakVuR9pxX4NM7JI → 60 mb PNG of best I could do. I’m aware of the blimp/ artifact.

In addition to the walking noise, you are seeing some banding that is typical of Canon cameras. What ISO did you shoot at?

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