Veil Nebula Processing Challenge

[Herzy]

Last night I got three hours on the Veil Nebula. It turned out better then I thought it would, but there are some strange gradients unlike what I've had to deal with before. It seems like they are all around the image (because the Veil Nebula is almost at the zenith) rather then in a single corner. I can't seem to get it to remove the gradients good enough so that I can stretch it to its full potential. If you all would mind giving this a go, that would mean a lot. Thanks in advance!

https://www.dropbox.com/s/rg1k9xkxf7dwiou/Veil Nebula - Full Stack (w%3Aflats).tiff?dl=0

In my process, I had to overdo the noise reduction a lot because my data is shallow and I had to run countless different modules in Startools to remove the background gradients. It looks okay when viewed form afar. When you take a closer look, however, it is really ugly and unnatural-looking. Here is what I managed from it: 

[alacant]

5 hours ago, Herzy said:

https://www.dropbox.com/s/rg1k9xkxf7dwiou/Veil Nebula - Full Stack (w%3Aflats).tiff?dl=0

Won't load in StarTools here's an uncompressed tif along with my effort. There's something in the top left and along the bottom that's making it hard to get st wipe to work properly. I cropped a long way; also need to mask maybe.... I'm sure the processing guys will be able to sort it. Otherwise I think it's a great shot. HTH

[Herzy]

5 hours ago, alacant said:

Won't load in StarTools here's an uncompressed tif along with my effort. There's something in the top left and along the bottom that's making it hard to get st wipe to work properly. I cropped a long way; also need to mask maybe.... I'm sure the processing guys will be able to sort it. Otherwise I think it's a great shot. HTH

Oh, sorry. Just realized I didn't convert it before uploading. The thing you were talking about was the reason I was having troubles removing gradients.Wipe kept leaving weird colors.

Great result. I like the colors and the way you tamed the stars down.

[alacant]

Hi. Thinking back to when I had something like this. I traced it back to light frame that I really shouldn't have included in the stack. I had a meridian flip and struggled to get re-centred: I notice a strip down an edge of the tif. Dunno. Worth a look? HTH

[Herzy]

1 hour ago, alacant said:

Hi. Thinking back to when I had something like this. I traced it back to light frame that I really shouldn't have included in the stack. I had a meridian flip and struggled to get re-centred: I notice a strip down an edge of the tif. Dunno. Worth a look? HTH

I had a meridian flip as well in the night and so I had to have two different stacks that I stacked together. I'll give it a look when I get home. What type of frame should I look for?

[alacant]

Anything that's different from the majority. Don't forget that they will be 180º mirrored e.g. mine was imaging during the flip; that frame will be easy to spot. Not sure what stacking you use but in DSS there's a thing called score. It gives an indication of good frames. Also try only frames before or only frames after the flip. There's no free lunch I'm afraid as even a 1 pixel wide stacking artefact is enough to throw the StarTools develop into a panic. HTH

[Herzy]

1 hour ago, alacant said:

Anything that's different from the majority. Don't forget that they will be 180º mirrored e.g. mine was imaging during the flip; that frame will be easy to spot. Not sure what stacking you use but in DSS there's a thing called score. It gives an indication of good frames. Also try only frames before or only frames after the flip. There's no free lunch I'm afraid as even a 1 pixel wide stacking artefact is enough to throw the StarTools develop into a panic. HTH

When I stack the individual groups (1.5hr before meridian flip and 1.5hr after) the gradient seems more easy to handle. It is only in the top left and has a sort-of radial blend to it, where as both of the stacks combined give an inverted vignetting effect (brighter on the edges). I don't understand how imaging over the meridian would cause that kind of effect, any ideas?