Help Processing Detail In Dark Nebula From DSLR RGB Data

what is the cause, or causes of flat fielding?

I am imaging in about as bad of conditions as you could possibly get as far as light pollution goes so it takes allot more exposure time to gather enough light to work with.
Ive actually tried stacking in few different methods. 1st was to stack the RAW images  in DSS using HDR  method and then also trying the Median method.

Then Instead of stacking RAW I also tried correcting each frame "white balance" "levels adjustment" ……. then saving each as .TIFF files and then stacking those frames in the same ways. Which actually seemed to work a little bit better than stacking RAW un-balanced frames.

For all stacking RAW Digital Development Process Settings Are brightness: 1.0, red scale 1.0, blue scale: 1.0 and then AHD Interpolation. With Black point set to 0
TY Jer

The one thing that I have not been doing, but will have to start taking the time to do is applying correction frames. Ive never really used darks, flats and biased frames. It's difficult when you have a limited time out to begin with. I barely have enough time to capture the light data that I do, though im going to have to find time to capture an equal amount of flat frames.

I'm assuming flats have to be taken each and every time out if you move your optical equipment at all. Even turning the focal reducer, or indexing the camera by a few degrees would make any previously captured flats useless. Or am I missing something.

Jer,

I was thinking of deleting this post. I know now you do not have PI.  I'm going to leave it though in case you decide you want to check it out with the demo version.

  Why not just process these images in that program from end to end?   My own experience is it does a far better job.   You have to make a master bias, dark and flat, then you go through a structured approach to producing your image.  The following is my basic approach and would work for your 12 hours of data.
1. Calibrate - clean up all frames with your master frames mentioned above.
2. Debayer - get color versions of the calibrated frames
3. Registration  - prepare for stacking
4. Integration - stack frames
5. Linear Fit -align color channels - a form of white balance is the best I can describe it.  It generates a new image at this point
6. Dynamic background extraction - get rid of your light pollution gradients and color casts - using the linear fit, DBE generates a new image - this is the one that you work with for the rest of your editing.
7. Multiscale linear transform - reduce noise

There is more, but the above gets your basic image.   The Light Vortex and Harry's Astroshed videos are very informative to get your workflow going in PI.

David

Hey Jeremy,
Knowing your imaging conditions, I must agree with the comments above. Calibration frames are almost as important as good lights. In you conditions the signal to noise ratio is pretty bad. Calibration frames will help clean it up. They can be taken at any time, not necessarily while imaging your lights. With the weather we have been having this winter and spring, any clear night is precious time for imaging  lights and cannot be afforded to be hated on calibration frames.

Darks can be taken any time as long as there are taken at or near the same temperature.  Same with bias. These are important to remove noise from the camera. On any long exposure, especially with an uncooled camera, the noise will increase with temp., and the longer the exposure the more noise will be generated from heat from the camera itself.  Subtracting the noise will dramatically improve your lights.

Flats will remove any defects in your imaging train. Dust doughnuts, vignetting, etc. It will also help with pulling out faint details such as the dark lanes in you Iris image.   When I started processing I was doing darks and bias . but not flats and I was asking the same question about my images. I found that flat  fielding was the answer. Of  all the gizmos and gadgets I have bought with this hobby, my Alnitak Flat Man was probably the best money I spent.

You can get good results with sky flats using a white tee-shirt over the objective. These grey skies we have had this spring are perfect to shoot flats. There are some good videos on you tube using this technique. These can be done anytime. no need to match the temp on these. Also if you try not to remove you camera from the train, or rotate it, you can reuse these over and over.

The same holds true for you darks and bias. You can use them over and over as long as they are at the same temp or close to your lights.

Clear Skies–MAYBE SOMEDAY!!!  

Bob