Cygnus Wall in SHO

[turfpit]

Captured Sept - Oct 2025.

Data: SII 8x450s, Ha 6x600s, OIII 8x450s. 100 bias, 50 each darks, 50 each flats. 3h integration.

Cygnus_Wall_SHO_SII-8x450s_Ha-6x600s_OIII_8x450s.jpg (562.28 KiB) Viewed 1897 times

Equipment: Vixen 81s, Vixen 0.67 reducer/flattener, Celestron AVX mount, Atik 9-slot filter wheel, Altair filters (SII=6.5nm, Ha=7nm, OIII=6.5nm), Atik 314L+ CCD camera, QHY miniguider & QHY5lII-M guidecam.
Software Sharpcap, Pixinsight.

Processing (PixInsight):

• WBPP for calibration and integration

• PixelMath to combine the channels, red = (0.9*SII+0.1*Ha), green = (0.8*Ha+0.2*OIII), blue = (0.9*OIII+0.1*Ha) from Charles Bracken's book The Deep Sky Imaging Primer

• GradientCorrection

• ScreenTransferFunction + HistogramTransformation to delinearise

• CorrectMagentaStars script

• TGVdenoise

• RangeMask

• LocalHistogramEqualisation with inverted mask

• CurversTransformation, slight 'S' curve and saturation

I did try processing with Starnet++ to create 'starless' and 'starsonly' but didn't really make any difference.

The data stacks:

SII_Ha_OIII_stacks.JPG (53.52 KiB) Viewed 1897 times

This is my first SII data - lots required.

For channel combination I also tried this formula I found in the PixInsight Forum:
R = (Oiii^~Oiii)*Sii + ~(Oiii^~Oiii)*Ha
G = ((Oiii*Ha)^~(Oiii*Ha))*Ha + ~((Oiii*Ha)^~(Oiii*Ha))*Oiii
B = Oiii

The Official PixInsight videos on Narrowband at https://www.youtube.com/watch?v=WYPVtmhXJYk were helpful.

My original plan was to exceed 10h of data but the weather .....

Dave

[timh]

I like that colour scheme Dave with the SII combining into the red along with HA. It is a more naturalistic way than Hubble of combining the colours while using all of the data and it looks good. I might go back and explore redoing some of my stuff in that way.

But I don't understand how the PixMath equation you found is normalising the data so will have to read up

Tim

[turfpit]

Tim

The formula was provided in the book but without any explanation. I did try a conventional ChannelCombination but the result was not as good (whatever good means with false colour?).

This is the HOO variant:

HOO.jpg (313.58 KiB) Viewed 1359 times

Dave

[turfpit]

Had another go at processing the HOO data.

HOO_final.jpg (759.53 KiB) Viewed 1264 times

These are the processing steps.

1.JPG (93.12 KiB) Viewed 1264 times

2.JPG (94.45 KiB) Viewed 1264 times

3.JPG (86.49 KiB) Viewed 1264 times

4.JPG (54.71 KiB) Viewed 1264 times

5.JPG (36.78 KiB) Viewed 1264 times

Dave

[turfpit]

A slightly different processing route for SHO. SII and OIII had many stars, Ha not so. Combine SII-starless, Ha and OIII-starless instead of performing star reduction later.

SHO_final.jpg (56.07 KiB) Viewed 1146 times

Evaluation: no amount of processing wriggling can substitute for lack of data - 10h planned but only 3h captured. The amount of stars displayed felt 'about right'.

Dave

[nexusjeep]

Hi Dave,
Have you tried the narrowband normalization process in PixInsight for mixing the channels I have found it works rather well it is what I used on the Soul image. Video of it below for info.

https://www.youtube.com/watch?v=n2h8jaAhsr4

Cheers
Nick

[turfpit]

Thanks for that Nick, I will look into it.

Dave

[turfpit]

Very useful Nick, thanks again. I got these with much less time spent on 'colours'. I went via the starless route with Starnet++, using Mode2 for the HOO variant.

SHO_HOO.JPG (58.83 KiB) Viewed 1033 times

Dave

[nexusjeep]

Glad it was of use; I have been trying Starnet++ and a 30 day free trial of StarXterminator and think StarXterminator is just edging it at the moment but need to try it on a few more image. I will however definitely be buying PixInsight and BlurXterminator as a minimum.

Now if only there was something I could by to guarantee clear nights other than moving to a different country or continent.

Cheers
Nick