DBE on lots of nebulosity?

[CharlesW]

Most DBE tutorials I've seen deal with a moderately sized Galaxy or nebula surrounded by lots of space. I just did 5 hours of the Rosette Nebula that fills about 97% of the frame. How do you DBE an image that is mostly nebulosity or do you DBE it at all? Is there a tutorial already in place?

[lucchett]

Hi,
Can you post a frame sample?
I did a first try on the same object at 1000 focal length and it was not easy.( for me...)

http://andrealucchetti.smugmug.com/Astrophotography/Astrophoto/i-2hWQz92/A

I can check if I retained the dbe process icon and share if you like to get it as a starting point, provided the framing is similar

In general, I try to find a very deep image as a guidance and put a few sample in the empty regions.
If you have complex gradients it will be hard, and optimal flats are required to easier things.
Andrea

[fulatoro]

Harry' s Astrished has a great tutorial on that. The second half of the tutorial deals with dbe on Nebulosity.

http://www.harrysastroshed.com/pixinsight/pixinsight%20video%20files/2013%20pix%20vids/dbe/dbe.mp4

[lucchett]

I may be wrong, but the issue with the image in the video is that in the area there is a "plateau" of faint nebulosity-dust. The samples in the lower right part (1/3 from corner) are risky in my opinion because they can possibly lead the model to cut this faint nebulosity.
If your image is very deep, this could be a problem.
In this case, you should try correcting your flats with super flats and compare the results to check if thre is further improvement for these areas.
Andrea

[bitli]

This is a difficult problem.  You can try to take just a couple of images of a dark area near the original location, preferably when doing the original image (maybe just before and just after to have about the same illumination), make a DBE on that one, and apply the generated correction to the original image, with some factor.  YMMV.  If you have some stable dust donuts or remaining vignetting not fully corrected by the flat, this may help. Sky gradient may be more difficult. 

In DBE you can force the value of the samples and use the DBE algorithm only to create the smooth image to subtract/divide. I used this with some script when I had other source of information on the problem (remaining amplifier glow), but this is lengthy to say the least and rely on your estimation of the correction to apply.

-- bitli

[Harry page]

Hi

Please let us see the problem image and then we can offer a solution

Harry

[topboxman]

Try ABE using default settings. It seems to work well on heavy nebulous objects.

Peter

[CharlesW]

I've attached my Ha master in 7zip. First time attaching an image here so hopefully it's useable. Thanks for whatever advice you may be able to give.

[Harry page]

Hi

This is a very small Image is this correct ?

Harry

[CharlesW]

Sorry for being such newb. Here is a Dropbox link with the full size xsif. https://www.dropbox.com/s/195grfudium8a1r/light-FILTER_Ha-BINNING_1.xisf?dl=0

[Harry page]

Hi

Being it a ha image you need very little DBE , like 5 samples 




Harry

[CharlesW]

Thanks, much appreciated.

[lucchett]

Harry,
I take the chance to ask a question on this, just to be sure.
I see you placed the samples in the best areas but nontheless there is still very faint nebulosity in these areas.
the model will consider this as gradient and try to flatten , right?
I assume this is not avoidable...
thanks for clarifying!
Andrea