Back to forums

Free Data to Process: Witches Broom 32hrs Broadband Data

Processing Deep Sky NGC6990 NGC Objects
7 replies•604 views
Fabian Butkovich avatar
Fabian Butkovich avatar
I've hosted several of these experiments before and always enjoy seeing what you all come up with! I have 32 hours worth of data on NGC 6990, or Caldwell 34, the beautiful witches broom nebula available for processing at your own will. The data itself is a mixed bag between different exposure lengths, filters and year. For my own rendition, I used PixInsights image integration module to simply average three stacks together, one for Optolong UV/IR cut, one for L-eNhance and one for L-Quad. However I know some people claim mixing various filters like this is redundant because of the narrowband nature of light pollution filters, it doesn't contribute to the final image when you integrate narrowband data with broadband data such as through an UV/IR filter. In total these are the integrations for each filter:


NGC 6990 (Witches Broom) Multi-Year Project

UV/IR: 7h
L-eNhance: 19.33h
L-Quad: 8h

I have made available all of the files from my PixInsight WBPP session, in which there are the 3 master lights. I used GraxPert for gradient reduction on all three individual before I imported them into PixInsight and processed further. 

NGC 6990 Fabian Butkovich



As always I'd love to know the detailed workflow and steps you used to better build my own understanding of processing. Below is a screenshot of all the various steps I used.

Good luck and happy processing!
Helpful Engaging Supportive
Oscar avatar
Oscar avatar
Here's my edit. L-Quad was not used, because I didn't know what to do with it. UV-IR cut was used for stars, and L-enhance for starless. Processed in PI and PS.

Fabian Butkovich avatar
Fabian Butkovich avatar
Oscar:
Here's my edit. L-Quad was not used, because I didn't know what to do with it. UV-IR cut was used for stars, and L-enhance for starless. Processed in PI and PS.


Thank you for your contribution! I really admire the strong colors of the stars but also they are very well tamed. I tend to overstretch the stars on most of my images, your version looks alot softer and more pleasing, it's hard to describe. I did re-do my own version with a more conservative stretch on both the nebula and stars and then re-blended everything together in Photoshop to get this result, which I like alot better. 

How did you treat the stars? Your stars also look like they have a soft glow around them, the edge isn't as sharply defined as in any of my versions. I usually sepeate the stars from the image very early on in processing, even sometimes with a first very gentile GHS stretch. Then I later may apply another gentle AsinH stretch to the stars before recombining them with the nebulosity. The AsinH stretch adds color.

I am curious, what do you use for noise reduction? the PI in-built ACNR? or NoiseXterminator?

Helpful Respectful Engaging Supportive
Dan Kearl avatar
Dan Kearl avatar
Here is mine.


Oscar avatar
Oscar avatar
Fabian Butkovich:
Oscar:
Here's my edit. L-Quad was not used, because I didn't know what to do with it. UV-IR cut was used for stars, and L-enhance for starless. Processed in PI and PS.


Thank you for your contribution! I really admire the strong colors of the stars but also they are very well tamed. I tend to overstretch the stars on most of my images, your version looks alot softer and more pleasing, it's hard to describe. I did re-do my own version with a more conservative stretch on both the nebula and stars and then re-blended everything together in Photoshop to get this result, which I like alot better. 

How did you treat the stars? Your stars also look like they have a soft glow around them, the edge isn't as sharply defined as in any of my versions. I usually sepeate the stars from the image very early on in processing, even sometimes with a first very gentile GHS stretch. Then I later may apply another gentle AsinH stretch to the stars before recombining them with the nebulosity. The AsinH stretch adds color.

I am curious, what do you use for noise reduction? the PI in-built ACNR? or NoiseXterminator?


Denoise was done first with NXT applied after a stretch on starless, then some Camera Raw NR; stars were processed almost wholly in Camera Raw (before moving to PS, I use BXT, and do a small histo stretch, just enough so that the core of the big star blends with the rays, and then some arcsinh after that in PI); Minimum filter was also used in PS

there is a lot of power in Camera Raw, especially for fine tuning stars to look like what you want; people just don't use it enough

thx for sharing your thoughts

EDIT: about NR, I also used masked convolution (strongest in the darkest areas, weakest on the brightest), however I wouldn't do that again because it was a real pain to disguise the noticeable mottling that appeared in the background
Peter Graf avatar
Peter Graf avatar
I also had a try with your data. I used the L-Quad for the stars (only) as it is a light pollution filter, but dropped the UV/IR data where the stars were little bit more bloated.

My steps were:
- GraXpert for background again, as there still seemed to be gradients, mainly for L-Quad
- BXT correct only, then BXT 0.25/0.00 + automatic PSF + 0.8 non-stellar sharpening. Not too much.
- NXT, also not too much. With v3 you can still leave luminance noise, which looks less artifically denoised. I think if there is noise, there is noise.
- SPCC on both images - for L-enHance if found these bandwidth settings: 10nm for Ha, 30nm for Oiii
- SXT to separate stars
- Stars image:
-- Seti Astro's Star Stretch script (default value 5.0, + some colour increase). it works ;-)
-- Curves for colour adjustment
- Starless image:
-- Stretching with GHS + Histogram + Curves

Then I put both together in Photoshop, with only some minor adjustments in Camera Raw (contrast, saturation), thought about rotating it by 180 degrees, and reduced it to 2000px width for uploading here.
The stars are more prominent, with BXT you can reduce them - also from a photo lens - to a certain amount. I also did not use SCNR, as Oiii to my taste has this greenish turquoise tint. SPCC should also have taken care of this to a certain degree.

It was fun to try something other than my own data. Maybe I should give my Nikkor 200-500 a try again... ;-)
Helpful
Neil McAllister avatar
Neil McAllister avatar
Here is my attempt at editing the data using Pixinsight.
Hornisse avatar
Hornisse avatar