How pink is your Sadr?

[Fegato]

Well, the weather here in South West Wales since the end of June has been appalling, and after a pretty good first 6 months of the year, I've struggled to get much imaging done. I normally just focus on broadband and moonless nights, but with a couple of vaguely clear moon-filled nights in September, I got the NBZ filter out and had a go with that.

I'm not so keen on very red Ha filled images, so the Sadr region was a bit of a challenge to process. In the end I decided to add some Hb to my Ha dominated image...  or at least, I did some sort of unscientific / random "Hb" addition. This pinkish image has 15% of Red (above Median value) added to the Blue channel. If not scientific, it was relatively easy to achieve. 

RASA 11 on CEM120, ASI2400MC Pro.  7 hours of 120s exposures across 2 panels with IDAS NBZ filter. 100 x 10s across 2 panels for RGB stars.

[CloudMagnet]

Brilliant picture, the pinks look really natural so I think your “random” addition has worked. It might be my monitor but I think the background is a little green? Might be worth adjusting the background levels to help the colour balance.

[Fegato]

4 minutes ago, CloudMagnet said:

Brilliant picture, the pinks look really natural so I think your “random” addition has worked. It might be my monitor but I think the background is a little green? Might be worth adjusting the background levels to help the colour balance.

 

Thanks!  I did SCNR some green out fairly late in the processing, but it was fairly light touch, so maybe not enough - I'll take another look when I can get some better light conditions tomorrow.

[Roy Foreman]

Nice rendition of the Sadr region.  Agree with you on the weather.  Here in west Somerset I've only had one decent clear night since June, and it's now mid October !

[Mr Spock]

Nice looking image. The green is very noticeable on my monitor though.

[Fegato]

12 hours ago, CloudMagnet said:

Brilliant picture, the pinks look really natural so I think your “random” addition has worked. It might be my monitor but I think the background is a little green? Might be worth adjusting the background levels to help the colour balance.

 

 

7 minutes ago, Mr Spock said:

Nice looking image. The green is very noticeable on my monitor though.

I've had another look this morning, and I'd obviously undone my SCNR at some point and not re-instated, so definitely some green. This might be a bit better?...

 

[Mr Spock]

Green is better balanced, but I'm picking up a colour shift in the background. I'm seeing a fairly consistent +-3 R:7 G:30 B:40 across the image's dark areas. Hope this is helping and not being a nuisance.

[Fegato]

10 minutes ago, Mr Spock said:

Green is better balanced, but I'm picking up a colour shift in the background. I'm seeing a fairly consistent +-3 R:7 G:30 B:40 across the image's dark areas. Hope this is helping and not being a nuisance.

No that's fine - I'll have a more considered look. I guess my PixelMath attack on the red has probably done more than I wanted it to!

[CloudMagnet]

10 hours ago, Fegato said:

 

I've had another look this morning, and I'd obviously undone my SCNR at some point and not re-instated, so definitely some green. This might be a bit better?...

 

 

Yeah, looks a lot better. Might still need a bit of reduction in both blue and green levels for the background. At this point, is likely more down to personal preference rather than science but its still an amazing image regardless

[Fegato]

Thanks @CloudMagnet and @Mr Spock for your comments.

I've been back through my processing, which has reminded me of the fact that you really shouldn't apply processes without understanding or thinking exactly what you're doing!  I use Pixinsight, and it is very rich in capabilities and as a result quite complicated. I like this, but sometimes need to take more care!

1. I was applying Background Neutralisation in a sub-optimal way, failing to use a proper background sample. I'd always done this properly until I started using Photometric and and now Spectrophotometric Colour Calibration processes. In redoing this, I found I'd actually neutralised a fair bit of faint nebula, as well as failing to get a good neutralised background.

2. Some of my stretches seemed to be affecting the background. The Script EZ Soft Stretch was a particular problem, and as this is no longer properly supported, I think I'll stop using it.

3. I still seemed to pick up some loss of a neutral background through stretching. Background Neutralisation is supposed to be run on the linear image, but I tried applying it on the non-linear image and this has done the trick. It also altered the colours across the image, but as they are sort of made up anyway...

Any expertise anyone can offer on maintaining a neutral background during Pixinisight post-processing would be welcome!

Here's the end result anyway. Not as pink, but a lot more faint nebulosity across the image.

Edited October 11, 2023 by Fegato
typo

[CloudMagnet]

On 11/10/2023 at 11:03, Fegato said:

Any expertise anyone can offer on maintaining a neutral background during Pixinisight post-processing would be welcome!

Here's the end result anyway. Not as pink, but a lot more faint nebulosity across the image.

 

I’ve never really used PixInsight for processing -I’ve always stuck to processing in Photoshop where colour balance can usually be sorted using a mixture of levels to balance black and white points along with Gradient Xterminator to get a uniform background. That’s always worked well for me. Comparing to existing images of the same target might also give an idea of how others have balanced out the colours before you go down your own route.

I think it just shows the value of processing an image more than once. I tend to do a rough first go at it to get a feel for the data and ways of bringing out details, before going back to the beginning and doing it all over again with what I have learned first time round.

The difference from where you started to now is really telling. I would say any further might be over-processed, I hope you are happy with how it turned out!