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Eastern Veil - NB Tricolour

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We were quite pleased with our snap of the Bat Nebula https://stargazerslounge.com/topic/280222-bat-nebula-eastern-veil-bicolour/ until, that is, we saw this masterpiece from Bill Snyder http://billsnyderastrophotography.com/wp-content/uploads/2013/11/Eastern-Veil-CFHT-Ha-OIII-SII-PS1-V4-CR.jpg

Mr Snyder had used all three NB filters, but it was not at all clear to us how he achieved the final result.  We captured a couple of SII frames and tried doing multiple different combinations and blends but got nowhere near.  So eventually @MrsGnomus  e-mailed Bill.  He got back to her fairly quickly and said that he started off with a reasonably conventional SHO (Hubble) mix.  He then started by following Bob Franke's method -  http://www.bf-astro.com/hubbleP.htm 

I got the SII - last night with a ludicrously bright 'supermoon' looking on.  It was noticeable just how much brighter our 'black' level was with the moon around even with the 3nm Astrodon filter.  Also the Veil is really getting a bit too low in the sky I think.  All told we got around 3 hours of SII last night to go with the 5 hours of Ha and 3 hours 40 mins of OIII.  I did a SHO combination - followed by the Franke method and then I got decidedly trigger-happy with the Selective Colour tool in PS.  I don't think I would be able to reproduce what I did.  I didn't get anywhere near the Snyder image, but the result was 'interesting'.  Our bicolour shot is better.  Nevertheless, I might try to get some better SII next year when conditions are more favourable.  

The main lesson we learned was not to try imaging during a near full moon even with 3nm filters.  (We simultaneously tried getting some 3nm OIII through our widefield rig - the individual subs looked OK but once processed, it was clear that there was a massive gradient running across the frame which DBE only partially eliminated.)


Comments and criticism welcomed as always - this is certainly more of a work-in-progress than a finished effort ....

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To be honest I have a bicolour version of this, and then recently I finally acquired some Sii to go with it.  When I put it together I did not like the result as much as the bicolour version, so I scrapped it. 

I think in your case too I prefer the bicolour version, somehow the Sii seems to make it less striking in both our images. 




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Hi Steve

So far I am with Carole the bicolour version was top drawer, SII has killed some of that lovely smoothness and detail you managed.  Maybe just a case of waiting for better SII.

Have you tried blending in PI?  I would start with -   R=s*.76+h*.24, G=h*.85+s*.15, B=Ox1.0 - Then SCNR (adjust SCNR to taste)

See what that looks like - I hope to have a go at part of the Veil my self shortly - no evidence the above will work, it just does when i try on most NB targets (can always tweak ratios a little if desired).  Unlike any PS method PI seems to blend it 'better' (that's today's technical reference covered :) )  




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I will try to 'Blend it like Gilliland'.  Let you know how I get on.

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Interesting point - I have all three sets of NB data ready to process in PixInsight but my previous efforts with the Veil (with Photoshop) showed a similar dilemma.  The SII just didn't improve it.  I have lots of data to process and an enormous amount to learn as I get to grips with PI !!

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If you already have the 3nm HII filter, then maybe give the [NII] a go as well. On the occasions I've tried I've seen more [NII] than [SII]. In fact, although I'm not sure I have the sub, when I was looking at the Eastern Veil last I tried a [NII] image and saw quite a bit of signal. Unfortunately the sky clouded over before I could do a proper run and I never got back to it as my house was getting in the way.

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