Strange vertical noise in DSLR frames

[Thorriz]

I have a problem in processing, where horizontal saw-like noises shows up if I stretch too far. These problems are also enhanced when I stack.

It's pretty strange, because I don't see them in my darks og bias. And I've tried to lower my ISO, but that didn't work either

 

I use an old and pretty worn Nikon D700

 

What could possibly be the cause, and is it possible to avoid? 

I've added two images: A single frame, and a stacked image (Both aggressively modified)

 

[BCN_Sean]

I've had this with a D700 as well, and the only thing I can work it out to being, though others who have more experience may have a better idea, is that the initial images are under exposed and the post-capture process is trying to pull out data that isn't there.

[ollypenrice]

If you have Photoshop then Noel's Actions (now known as Pro Digital Astronomy Tools) has a very powerful 'remove Vertical Banding' routine.

Large scale dither between subs would probably be a big help as well, 12 pixels or so.

Olly

[Thorriz]

Okay. Thanks for the tips! 

I don't have photoshop, but at least I know what's i called now  So I might be able to find similar tools. Until then I'll try to get more exposure. 👍

[Nigella Bryant]

1 hour ago, Thorriz said:

Okay. Thanks for the tips! 

I don't have photoshop, but at least I know what's i called now  So I might be able to find similar tools. Until then I'll try to get more exposure. 👍

Try dithering too. It averages out the banding. 

[Thorriz]

I saw Olly mention it too. I'm not that experienced, so I had to look it up what it meant. But it sounds like a really good idea. in my case. So again, thanks for emphasizing its importance  

[Nigella Bryant]

I found out by accident that dithering works, lol. 

[ollypenrice]

12 minutes ago, Thorriz said:

I saw Olly mention it too. I'm not that experienced, so I had to look it up what it meant. But it sounds like a really good idea. in my case. So again, thanks for emphasizing its importance  

It's hugely effective for DSLR imagers. It really is.

Olly

[edarter]

What are you stacking with? I had bad horizontal banding with my eos600 that I tried everything I could think of to eliminate. The shorter the exposure the worse it was/is. 10s exposures for plate solving are still horrid. 

However, I switched from DSS to APP for stacking and that helped massively, I also now typically take 240s subs since starting guiding which ensures the data is above the background noise of the sensor. 

[alacant]

7 hours ago, Thorriz said:

What could possibly be the cause

Dark frames. Try without? If you do use them, make sure that bias has been subtracted and that you have a decent dark optimisation algorithm in place.

If it persists, the best way is to remove the banding before registering and stacking the frames.

The best we've found for both is Siril; even the most stubborn old camera banding succumbs. 

With DSLRs, dithering really isn't optional.

Cheers

Edited February 6, 2021 by alacant

[Thorriz]

Again, thanks for the replies. Haven't been able to find anything Siril. I think the website might be down.

Haven't tried APP, but I'll give it a look.

 

Anyway. Finally got a clear sky. So I tried to boost the signal by upping my ISO and aperture. I also took a few images, then moved the target a bit with the hand-controller.

And my end result was pretty good by my standards. I really need a better lens though. Focusing is near impossible.

 

Another thing to mention. I did a bit of read on Deep Sky Stacker, and learned that when you have a low signal. Too many darks can have a negative effect - pretty much what you suggested Alacant. So this image I only used 3.

 

Here's my first run though of the data. I think I will redo it. Got a nasty orange flow and got I too aggressive at some points. But the main thing is hardly any banding.

 

Only got 78 x 30s subs because I knocked my mount when changing the battery on the camera. Yay

ISO 1600, 3 darks, 4 bias, Nikon D700, 70-300mm Sigma Lens ø55, at 300mm

Nexstar 4SE mount, "polar aligned" using the wedge - I got lucky

 

 

[alacant]

32 minutes ago, Thorriz said:

Haven't been able to find anything Siril.

Hi. Well done on the image.

Siril is here.

HTH

 

Edited February 11, 2021 by alacant