Strange banding?

[Phillyo]

Good evening,

So I've started seeing some banding on my stacked and calibrated images that have only shown up in the last set of data I collected. Could this be EMI induced? Please see image attached as an example. It shows up whether I calibrate my data or not so it's not a darks/flats issue I don't think.

Thanks!

Phil

[pipnina]

I think it's shown up for me before in image stacks. Maybe try adjusting rejection methods in calibration / light frames and turn off any drizzling if you use it?

I don't know why it happens, but in one set of data where it occurred in DSS, it didn't occur in Pixinsight.

[ONIKKINEN]

What about without star removal? These kind of look like artifacts that early versions of starnet++ produced when the kernel/cell (forget what its called) size was improper, although didn't see banding exactly like this so a long shot.

[Phillyo]

7 hours ago, ONIKKINEN said:

What about without star removal? These kind of look like artifacts that early versions of starnet++ produced when the kernel/cell (forget what its called) size was improper, although didn't see banding exactly like this so a long shot.

I used the new StarXterminator, and although it's hard to see them, they are still visible without star removal  

[Phillyo]

Interestingly I've just stacked them all together again without any calibration, no banding. I've stacked maybe 20 of them with calibration files, no banding...!? I'm now stacking them all again, with calibration files to see if the banding is there. If so I'm going to assume that one (or more) of the light frames have banding on the images, but not all of them.

The plot thickens!

[Phillyo]

Stacked them all and the banding is there so it must be present in one or more of the light frames. Now I need to find out which one(s)!

[scotty38]

I don't know how or why it only affects some but it "feels" to me as more of an acquisition problem. I have read about changing the USB limit, could be worth a try????

[Budgie1]

Just a thought but, you say you stacked them all without the calibration frames and there was no banding, but there is when the calibration frames are added to the stack?

What calibration frames are you using and have you tried only stacking, say Lights + Darks, then Lights + Flats, Lights + Darks + Flats, Lights + Darks + Flats + Flat-Darks? If there's an issue with one set of the calibration frames then this could be causing it.

Also, if you're using BIAS & Darks then try using Darks & Flat-Darks instead. With my ASI294MC Pro I had artefacts from the amp-glow left behind when I used both Darks & BIAS, so I now use Darks & Flat-Darks only.  

[Xsubmariner]

I experienced some similar horizontal banding with one of my IMX camera’s and found the flats were at fault. Sometimes with very short exposure  times the banding showed up when viewing the flats stretched. Quickly resolved by retaking the flats with longer exposure after inserting a couple of paper sheets between the flat panel and telescope.

[Phillyo]

Thank you all.

The testing continues. It isn't the light frames, so it must be calibration frames somewhere. It's strange that this is only happening with this set of data and wasn't apparently with the last set which was the same settings etc. I might take some more flats/darks, but until then I'll do as Budgie1 suggests and stack them in groups to see which is the culprit. 

I don't use bias, I use flats and dark flats with timings of around 4.3 seconds (both of them match) using NINA Flats Wizard.

Phil

[Phillyo]

It looks like it's my calibration files, specifically my darks, that are causing the issue. Very strange as I've only just taken them! I guess I will try to redo all the darks, flats and flat-darks again later and see how that goes.

Phil