Weird Artifacts in RGB Linear Image

I am seeing some weird artifacts in this RGB image. They’re also in the linear RGB as well. Anyone know what’s causing this? The red, blue and green color spots on the left side of the image are something I’ve never seen before.

📷 M53 & NGC 5053 RGB Non Linear_1.jpgJerry

Imaged with ZWO ASI2600MM and Astronomic R, G and B filters. Bortle 2, good sky conditions. 7,500 feet altitude, Askar 130PHQ scope.

*I exaggerated the weird blotches by over stretching the image, and they’re not hard to hide, but they should not be there. I pre-processed these in Pixinsight’s WBPP, processed in PI and post-processed in ACD Photo Studio.

180” exposures, a bit over 28 hours of exposure time. Gain 100.

HI, Jerry.

Can you tell which equipment you have and also the camera settings, etc?

Interactive Sky · Mar 19, 2026, 05:35 AM
HI, Jerry.
Can you tell which equipment you have and also the camera settings, etc?

Equipment and more info has been added above.

Jerry Gerber · Mar 19, 2026, 05:38 AM
Interactive Sky · Mar 19, 2026, 05:35 AM
HI, Jerry.
Can you tell which equipment you have and also the camera settings, etc?
Equipment and more info has been added above.

Oh, I see — I just didn’t notice that earlier.

Sorry for bothering you.

I’ve actually seen similar strange artifacts during long integrations, especially after background extraction and denoising.

In my case, I was using GraXpert, and saving the image with GraXpert Stretch usually helped reduce or remove those “weird blotches”.

Interactive Sky · Mar 19, 2026, 05:51 AM
Jerry Gerber · Mar 19, 2026, 05:38 AM
Interactive Sky · Mar 19, 2026, 05:35 AM
HI, Jerry.
Can you tell which equipment you have and also the camera settings, etc?
Equipment and more info has been added above.
Oh, I see — I just didn’t notice that earlier.
Sorry for bothering you.
I’ve actually seen similar strange artifacts during long integrations, especially after background extraction and denoising.
In my case, I was using GraXpert, and saving the image with GraXpert Stretch usually helped reduce or remove those artifacts.

📷 image.png

Something moving and slowly rotating across the field.

These could be hot pixels. They move around with dithering, forming clouds that look similar to this. It might mean you just need new dark frames, which normally cancel these out, unless new ones have recently developed. If you are confident you used dark frames made recently, then I’m flummoxed, as well.

Do you see this artifact on the master flats?

I’ve seen stuff like this when a bright star shows up on sky flats that are taken after sun down.

📷 image.pngSay Hello to Polaris, it was up when I took sky flats.

Hi, Jerry.

+1 to Andrea’s suggestion, at least for those on the RHS of the image.

Given that they are all in a straight line, it is more likely that something (e.g. satellite or aeroplane) has moved across the field during one of the exposures. If that’s the case, it would likely only be in one sub, which should be possible to identify and either confirm or elimate as a likely cause - (28hrs at 180” is only 560 subs 🙂)

If this happens in the same location on all (or many) of your subs/images then there would be something more systemic going on but I think you’ve only asked about the one image.

Cheers.

Paul

James · Mar 20, 2026, 08:46 PM
Do you see this artifact on the master flats?

I’ve seen stuff like this when a bright star shows up on sky flats that are taken after sun down.

No, no artifacts on master flats and no artifacts on subs coming directly from the camera uncalibrated. I think it’s likely Dave Rust is correct as I haven’t renewed my darks in about 2 years. As soon as there’s a cloudy night and the observatory roof is closed I am going to take new darks. I hope that’s the cause.

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