NGC 6960 Veil Nebula in HOO. Tips appreciated!

[pipnina]

I'm still quite new to narrowband imaging, still trying to work out how to process it all.

This represents about 90 minutes of Ha and about an hour of OIII

My current workflow is to perform gradient extraction on each filter master light individually, then LRGB combine and begin stretching R, G and B separately trying to keep the background neutral while bringing out the nebula in a bright and clear way. Then I fiddle with the curves, editing RGB separately and with the same aim as when stretching. Eventually I move to RawTherapee for final touches, some denoise and wavelets.

Any tips for improving my process are welcome! At the moment it seems a little blue, but I am struggling to make the reds seem as deep as the blues, they look a little purple-y, and the background is either blue, green or red and I can't make it go grey.

Hoping to get the other half of the veil soon!

 

[tomato]

Really clear and crisp. There is a hint of red in the background, but that may be the iPad I’m using to view it.

[old_eyes]

It's nice image. Lots of detail in there.

My initial process had the same red/purple cast.

With a bit more effort, I reached this version

I processed mine in Pixinsight, and I can't remember exactly how I got from the initial image to this final version. However, I definitely cropped the Ha and O3 masters to get rid of any edges. Any mismatch between the masters can create problems when removing gradients, and I see your image does need trimming. I then did a careful Dynamic Background Extraction to remove any gradients. Masked Stretch to get non-linear images that were then combined into HOO/RGB. At that point I still had the red/purple issue, but working on the colour balance with Curves Transformation gave me something I was happy with.

It is, in the end, all a matter of personal choice with narrowband. So just keep playing until you are happy. I suppose my point is that I started with pretty much the same image as you did, so it does not have to stay like that. You can shift it to where you like it best.

Good luck!

[MKR]

On 08/08/2022 at 16:05, pipnina said:

Any tips for improving my process are welcome! At the moment it seems a little blue, but I am struggling to make the reds seem as deep as the blues, they look a little purple-y, and the background is either blue, green or red and I can't make it go grey.

I've had this problem recently with my first NB image. I stretched Ha and OIII separately first, keeping the dark point similar on both parts, then combined them. The way I fixed the tint (not purple like yours, mine was red) was to stretch further OIII while still keeping the same black point. Iterated this a few times, each time combining the two images into RGB to visually assess the result. It's a bit hand wavy, and I don't have any more scientific procedure for this yet. I'd love to hear someone's more experience workflow.

[old_eyes]

@pipnina I took the liberty of downloading your image and seeing if I could give it what to me feels a more pleasant rendering (remembering all this is personal opinion).

I used a trick I find useful when NB images have purple star haloes. You invert the image - that makes the purple appear green. Then you use SCNR to reduce the green. I applied SCNR at 50% and then 20%, and invert again to get the original back with less purple. Then I reduced the saturation slightly and tweaked the overall luminance curve to get this:

It is a version that suits my taste better, it might not be to your taste, but this was about 10 mins fiddling around with the image. Nothing fancy. The available tools can do almost anything to an image and you just have to have the confidence to plunge in and make mistakes.