Veil Nebula SHO - processing in PixInsight to use all 3 filters

[TerryMcK]

Previous incarnations that I have done of the Veil are usually in HOO which is the traditional way of representing a supernova remnant or playing around in SHO and getting garish results.

The nebula is full of sulphur as well as Ha and oxygen III and I was looking for a new way to utilize the red of the S2 along with the Ha (which is also red) and mapping to RGB.

Then last night I was on a live stream where Adam Block happened to demonstrate a well known method (which I had forgotten) on how to do it.

So here is my SHO representation done in PixInsight.

 

• William Optics Redcat 51
• ZWO ASI 183MM Pro
• Baader 3.5nm Ha filter and 4nm O3,S2 filters
• 38x 360 seconds O3
• 91x 360 seconds Ha
• 43x 360 seconds S2
• Gain 111 Offset 8

Total 17.2 hours from Bortle 7/8 26th August 2022 to 2nd September 2022

 

 

 

Here is my processing for anybody how might be interested

 

• First of all working in linear mode use StarXTerminator to remove the stars from each of the monochrome images
• Next do linear noise reduction using whatever method you choose. I use NoiseXTerminator
• Then using PixelMath use this formula, after renaming the images to S, H and O respectively of course, to create a linear RGB image

// R:
H+S

// G:
2*O+H*0.3

// B:
2*O

 

• Do some Dynamic Background Extraction as the colours might not be to your taste
• Then do a histogram transform to change it to a non linear image.
• Do whatever else processing to your own taste

• I then went back to the original mono images, converted then to non linear after combination and extracted the stars.
• Then simply added them back together with about 80% of the stars.
• Did a star de-emphasize using the excellent AstroSwell script (Star De-Emphasizer) and here the above image is my results.

 

 

 

[Sonyme]

Very nice Terry. Lovely colour balance and even though there are a lot of stars in the background they do not overpower the image.       Gary

[TerryMcK]

32 minutes ago, Sonyme said:

Very nice Terry. Lovely colour balance and even though there are a lot of stars in the background they do not overpower the image.       Gary

Thanks Gary.

[P Holdsworth]

Very nice image and processing Terry. I really like the colour balance, composition and star reduction. I would imagine this is a great target for your redcat 51 with its field of view ? . 

Cheers Paul

[Astrobdlbug]

Terry, really like what you have done with the Veil and the processing.

I watched that video recording on YouTube  and Adam really explained the concept extremely clearly.

I agree with you that the veil has structural detail contributions from all three channels and a colour mix overlaid to a Ha luminance would not deliver the detail.

 

The teal/red combo you have presented  is very easy to interpret - wonder - are you temped to try out the modifier mixes that Adam presented in same video ?

 

Its definately got me thinking in a different way about how to process narrow band and if there is enough good data in each channel then I will try to stop using the Ha channel as a luminance - but the caveat akways here in UK do we get enough time (clear skies) on a single target to use the 3 channel flow......

 

Bryan

 

 

 

 

 

[TerryMcK]

Thanks Bryan. I think I will have a go at the modifier mixes too. Adam certain presents really well.

I still like adding Ha into luminance but it does depend upon the subject. Experimentation is the key with PixInsight and it is a very powerful piece of software.

[Dmack1]

I really like that Terry. The process seems to bring out the central filaments. Nicely done

 

David

[TerryMcK]

For those interested in the AIC (AstroImagingChannel) presentation by Adam Block used by me and Bryan @Astrobdlbugin our respective images - Bryan's one is his Elephant Trunk Reprocess thread here 

Then the AIC link is here 

 

 

[TerryMcK]

Same data as before but processed with modifiers to bring out the sulphur. Garish, yes and probably needs taking back a bit (quite a lot actually if I'm honest) but a bit different from the traditional SHO combination.

 

My pixelmath combo on this was 

// R:

h_starless + s_starless*(hs_modifier+1)

 

// G:

h_starless*3 + 2*o_starless*ho_modifier

 

// B:

2*o_starless

 

Really want to change the magenta to a deeper red so might do that in a different iteration.

 

 

[Astrobdlbug]

yes more tweaks I think - it took me quite a while to tailor the modifier images and also the mutiplier factors in the equations. Are you using linear or stretched images ? 
with stretched the 2*o_starless is way too much and the multiplication factor for ha_starless in the G channel I pushed back to 0.1 ( I don’t think you meant 3x there above it was 0.3 in the video)

I think every image will need custom values to achieve a pleasing colour mix with this technique

Bryan

[TerryMcK]

Linear Bryan. 0.3 produced awful images certainly on this target probably due to the strength of the data I have. At 0.3 it was like a neon sign. I'll post some examples when I get chance.