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M42 in Narrowbands...

fatwoul

By fatwoul
in Imaging - Deep Sky

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fatwoul

fatwoul

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OK, I already posted this, but in an admittedly rather unhelpful thread of different junk. So here it is seperately. M42, shot in the (painfully) early hours of Saturday

x14 H-Alpha, 240 sec:

M42HA.jpg

x9 OIII, 240 sec:

M42OIII.jpg

and x9 SII, 240 sec:

M42SII.jpg

Combined in HSO configuration (R-Hydrogen, G = Sulphur and B = Oxygen), to give this:

M42Colour.jpg

The final result is a little lurid, but that's just how it popped out of Photoshop after I put the narrowbands into the channels.

I thought I'd post the original images this time. If anybody who shoots OSC or with a DSLR fancies a go at playing with some narrowband images, and trying different configurations (HOO, or Hubble, for example) they're most welcome to do so.

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fatwoul

fatwoul

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Thank you. It just occurred to me that, while I thought I knew what the trapezium was, I'm now not sure. I thought it was the little group of stars in the core, but is that right? Or perhaps the overall shape of this part of M42?

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fatwoul

fatwoul

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How's this ?

Really nice. Much nicer than my clumsy attempt, that's for sure. Thank you for doing it.

Greyscale images mapped to CMY and the full colour mapped to K. Contrast enhanced and then back to RGB...

Oooh! I'm so glad you did this. It occurred to me a while ago to try working in CMYK instead, after I first started reading about using a luminance channel, etc. Your lovely result has convinced me to try it myself.

I don't suppose you got a luminance layer did you?

Alas no, although to be honest, with my skies I'm not sure how helpful it would be - without any colour filtration the orange glow kills a lot of the detail here. :)

I'm definitely going to come back to M42 several times while I have the chance, because it's such a nice target for a newbie like me to practice on, so I'll make sure to blast away some L next time I'm out.

Thanks again, that looks marvellous.

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blackparticle

blackparticle

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To be honest, I wouldn't have thought of CMYK unless I'd just been on about it in Olly's post.

You may have the same issues with burning out the core with luminance unless you do a run of shorter length subs as well and do an entropy weighted stack in DSS or run it through the HDR process in PS.

Depending on which way around you map the CMY some interesting results are possible.

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fatwoul

fatwoul

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You just baffled me a bit with the entropy weighting. I have to admit my processing is woefully inadequate, and something I really need to catch up on. I often feel like all this lovely kit and the subs I'm producing are being let down by my lousy ability to use them. I'm making that my winter project for cloudy nights. I'll give CMYK a try on this one, and on my Pacman data from earlier in the year. Ooh and I've got some Bubble data I could try it on. Playtime...

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blackparticle

blackparticle

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As far as I can tell, the entropy weighting method tries to average out the data into a HDR image and do an amount of stretching for you. It seems to work best if you've got subs of different lengths or differing amount of sky-background noise by analysing the difference between high and low contrast points and weighting them accordingly.

So the wispy bits on a 20 min sub would take preference over what would be a flat nothingness on a 1min sub and the contrast on a 1 min sub would take preference over the burned out section of a 20 min sub.. That's the theory anyway. It doesn't always produce great results but it's worth trying.

You might be able to simulate a HDR luminance layer by entropy stacking your Ha, SII and OIII together in one go. Worth a shot I think.

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fatwoul

fatwoul

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Stop stealing my thoughts, bp! As I was shoving my subs through DSS at the weekend, and I noticed that the SII had all the core detail, I wondered what it would look like if I put them all through as one image. They're all the same length anyway, so different sub lengths wouldn't come into it on this occasion. I had no idea entropy weighting might be useful for this. I'm going to try it. Thanks again.

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