New camera - strange noise pattern

[avid.astronomer]

Although I've been playing with afocal AP using my phone for quite a while, I recently acquired a ZWO ASI224MC camera, which I thought would take my images to the next level. On planets, it has indeed performed admirably. But whenever I try to stack full-frame images for some of the bright DSOs, I strange glow appears around all four sides of the picture. The more frames I try to stack, the worse the glow is.

Here's an example image.

I took this last night. I screwed on the included fisheye lens and captured about 1000 1-second exposures of the sky over my house and then stacked them with Deep Sky Stacker. Ignoring the lens flare from Mars (probably a bit of dew on the lens), the gradient around the edges seems much too uniform to be light pollution. I'm guessing it might be amp glow from the electonics being too warm, but I'm certainly no expert in this area.

Does anyone know what is causing this and how to eliminate it?

[bobharmony]

Interesting, Tom. It almost looks like flats overcorrecting but I'm guessing you haven't used any flats. Did you use any calibration frames?

Bob

[avid.astronomer]

Interesting, Tom. It almost looks like flats overcorrecting but I'm guessing you haven't used any flats. Did you use any calibration frames?

Bob

Thanks, Bob. No, I haven't created any flats yet. I tried darks on similar images and that helped a bit but it was still a mostly unusable image. I think I'll read up on how to make flats and create some and see if that helps.

If this is fairly normal for raw camera stacks with no calibration frames, I'm more than happy to learn the process of making darks, flats, etc. But if it's an issue with the hardware, I don't want to be banging my head in post-processing for no reason.

[Graeme1858]

Hello Tom

It's amp glow. My ASI294MC does a similar thing.

Dark frames completely correct it. (Even just 5 or so)

Regards

Graeme

[Larry 1969]

I thought amp glow was on one side of the sensor.
Does it produce images like that without the fish eye lens?

Larry

[Graeme1858]

I thought amp glow was on one side of the sensor.
Does it produce images like that without the fish eye lens?

Larry

Ah! I was thinking about the artifact on the left. The glow all round is not amp glow!

Does it only happen with the fish eye lens in place?

Regards

Graeme

[UlteriorModem]

Field curvature?

[Gordon]

To me, it appears to be a 'glow' from the light pollution in your area. It's 'sort of' even but lesser towards the left (less light pollution). Stacking the images would just compound the problem. Try taking a series of images "out of focus" and use them as flats. Use the same exposure time and gain settings. That should give you something to work with as flats.

[Graeme1858]

Here's some amp glow!

Regards

Graeme

[avid.astronomer]

Thanks for all the helpful responses! I've been in touch with ZWO (not an easy feat, as their tech support is in China and the time zone difference makes for a long delay in communications). They had me take a few dark frames with my lens cap on and send to them, which I did. Their response was that the camera seemed to be performing normally and it was probably light pollution. Not exactly a satisfying answer, but they may well be correct. I really don't know enough about the imaging process yet to dispute it.

[UlteriorModem]

It almost looks like frost but yea I know it's not a cooled camera.

[Star Dad]

That looks to me like vignetting. I have the same problem in Bortle 4.5 skies using the ZWO ASI294MC Pro. I use StarTools for post processing and by using the vignetting setting and a 2-pixel dark anomaly setting it completely removes it.