ABE or DBE Image Problem

[morgandollar1]

I've been trying to figure out what my processing problem has been for months now. I have read everything I can find on the internet and have watched countless videos on this situation but can't solve it. I use a Meade 10" RCX400 SCT at prime focus with a Nikon D810a DSLR camera. I can load and process my images with no problems. I shoot DSO like galaxies, globular clusters and nebula and always capture the targets. My problem is that no matter how I process the images when I perform the ABE or DBE I get what looks like circles of light or most of my image field filled with light. At first I thought it was my mirrors in the scope so I took them out and sent them in for recoating, still waiting for them to come back. While waiting I put my camera on my scope by piggyback, with Nikon lens, and I am getting the same results. I then thought maybe its my camera so I got a new Nikon D810 and it still has the same problem. I also thought that maybe its the light pollution at my site, suburb of Chicago, but as you will see in my images its not consistent. Usually the vignette areas have a nice black background and the center has the issue but other time there are areas in the middle or on one side. The vignette or dark areas in the following images have the perfect appearance but the rest is the problem, what is it? Please look at these sample images and tell me what to do next. I have found that I can use range selection and use a mask to remove this light but that also takes away part of the target detail. I always stack multiple images, have tried flats, bias and darks with the image but always the same results. This has been driving me crazy for months! Please help if you can.
Brian
I tried to attach pictures but it said they are to large. How do I add pictures to this forum?

[pfile]

you can upload the pictures to google drive, or some other cloud host and then put the link here in your message.

rob

[morgandollar1]

I figured out how I could pictures. The first set is of problem examples. The 2nd is a before and after of ABE. What is this apparent light in the image?

[pfile]

something is very wrong with those first two images. those are right off the camera? or they are calibrated? if calibrated i think your flats must be bad.

the vignetting is very unusual. are you using any kind of focal reducer.

rob

[morgandollar1]

Rob,
  No focal reducer or calibration. I take from 15 to 30 images at 60seconds. Perform star alignment and then image integration. It comes out as a normal image when stretched but then I apply the background extraction and this fuzzy, light, cloudy stuff is left behind. The background is removed because I can see it in its own individual window. Its almost like my camera pixels are picking up traces of light but I have no idea how. I'm willing to try any ideas you may have.
Thanks
Brian

[pfile]

hmm, so im a little confused, is one of those images pre-ABE?

i suppose its possible you have stray light entering the light path somewhere. do you have the eyepiece of the camera covered up? that's a common place for light to get into the camera...

rob

[Duncan]

I figured out how I could pictures. The first set is of problem examples. The 2nd is a before and after of ABE. What is this apparent light in the image?

Hmm. So it looks like these are aligned and then integrated, but without flat calibration, is that correct?

In the first two images, I see what look like dust shadow artifacts moving across the image, meaning that there's a significant translation across the set of images that it being tracked when aligning.

I'd look first at the calibration process. You mentioned earlier that you captured flats. Could you maybe upload a set of raw lights and flats to dropbox (or similar)?

[morgandollar1]

Rob,
  In regards to stray light. I was thinking about the same thing early on so I flocked the focuser, adapter optical train, inside of scope and dew shield. Same result. I then rolled up a piece of black paper and put inside the rear of the scope and into the face of the camera. The center had the same issue and the vignette was clean and dark background. Keep in mind that after those attempts I took the scope out of the situation by putting the camera piggyback on the scope with a camera lens and still same problem. View finder is closed. What I would like to ask is if you took images and just star aligned and integrated would your pictures have a dark background after ABE? Is it a setting in the PI software that I am not setting for my DSLR? Why do the vignette areas in my images look so perfect and the centers look so bad?
Brian

[morgandollar1]

Duncan,
  I saw those same shadow lines which you called a significant translation. What is that?

[Duncan]

Duncan,
  I saw those same shadow lines which you called a significant translation. What is that?

Normally I would expect to see donut shaped shadows in the image that are caused by dust. These should disappear with flat calibration.

If you have shifts in the image from one sub to the next, alignment will take care of this, but also mean that the dust donuts will appear to move from one image to the next, resulting in a smeared dust artifact in the stacked image. What I see in your images looks like that kind of effect.

I think what you need to look at is the images before stacking and before and after calibration; based on your results I think you either have stray light getting in somewhere or, alternatively, something very wrong with the calibration process.

Regards
Duncan

[Duncan]

Additional: the "smeared/translated" dust donuts show up in the first pair of images. In the second pair, the donuts appear stationary, and greatly amplified by the ABE process from left to right.