Hubble Bubble

[DaveS]

Toil and Trouble, much of both!

This data was captured on 5 nights between the 22nd June and 19th July in 900 sec subs with the ODK 12 / G3 16200 combination with 3 nm Chroma SHO filters. 12 Hydrogen, 16 Oxygen, and 16 Sulphur subs made it into the stacks after chucking out the worst subs.

Calibrated with Pre-calibrated Flats and Darks.

Initial SHO combination and cropping in AstroArt 8, then into PI for BlurX and NoiseX, then back to AA8 for DDP and colour adjustment

Saves as a JPEG

I'm still not happy with it despite spending many hours bashing with the heavy hammer.

Given that I'm out of practice with NB (Been concentrating on galaxies for the last year or so) any advice will be welcome.

Thanks for looking.

[Elp]

Looks okay. Did you try starless processing as you can normally push the data more. A green noise removal will also give you more of the Hubble pallet look but obviously removes a lot of the "good stuff" hydrogen signal.

Edited July 24, 2023 by Elp

[DaveS]

No, I didn't try starless processing, as that's something for me still to get to grips with. I used several iterations of the "Attenuate One Colour" tool in AA8 with careful note of the processed areas, as the original image had both too much green in the target area and a huge magenta area around the outside, plus the usual magenta stars.

[Adreneline]

26 minutes ago, DaveS said:

any advice will be welcome.

Ah, the captivating Bubble - it's a real challenge!

This is all down to personal taste but this is what I achieved:

Looking at your image there appears to be some back ground gradient - like vignetting - which is not helping to achieve a flat background.

I applied ABE to try to flatten it best I can and then super-stretched the mask so you can see the problem.

I used SCNR 90% to reduce the green cast. I also inverted the image and used SCNR 100% to remove the magenta.

I used an L mask to reduce the noise (and I am bound to have lost some detail as this is a jpg) and I also carried out a tiny bit of sharpening to try to ameliorate the noise reduction.

I created a second L mask and boosted the gold and the blue a little.

Colours are all down to personal taste and I am not a fan of green or magenta but quite understand some members like to retain the green Hubble'esque look.

I hope this is of interest.

 

[DaveS]

Hmm... I may have left too much green in the image when I was taking it out as I wanted to avoid sending it too red. I may have another go.

I'll have a go with ABE to see how much vignetting there still is, I thought the Flats would have taken care of that. I ran NoiseX but kept the level to 60% as I didn't want the background to go too "plasticky".

[Adreneline]

1 minute ago, DaveS said:

I may have left too much green in the image when I was taking it out as I wanted to avoid sending it too red. I may have another go.

It's a difficult balancing act between removing green cast and not reducing green too much such that it throws off the RGB histogram balance.

This is your original with histogram...

... and after applying SCNR ....

The peaks are now slightly better aligned and the relative differences have been reduced and the balance has been improved.

2 minutes ago, DaveS said:

I thought the Flats would have taken care of that.

Tricky things flats! I've had lots of fun and games (Not!) taking flats that do the job properly and actually produce a flat image.

4 minutes ago, DaveS said:

I ran NoiseX but kept the level to 60% as I didn't want the background to go too "plasticky".

I was trying to reduce this - which I suspect is jpg artefacts rather than anything else:

 

 

[DaveS]

Thanks for taking the time and trouble over this.

I'm going to take a pause, have a think, and come back with fresh eyes.

[DaveS]

I duuno...

Had another play with this through PI and AA8. SCNR in PI, then DDP, residual magenta removal, and curves in AA8

Still not happy.