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Elephant's Trunk (IC1396) - Narrowband (HST)


strutsinaction

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Hi

Finally got round to processing my IC1396 (Elephant's Trunk Nebula) data that I acquired a couple of weeks ago. This is my first attempt at mapping NB data to the HST palette. Quite tricky reining in the Ha (green channel) but I'm happy with the result.

Details:

Ha 12x600s, OIII 12x600s, SII 5x600s, all 1x1 binning, plus bias and flats. Processed with PI.

Regards

John

post-1421-0-38599700-1434316119_thumb.pn

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Lovely image John.

I use SCNR with practically every image and it is a staple process in my PI workflow.  I sometimes find that I need to use the HT tool to adjust the individual channels to better balance the NB colours for the popular palletes.  You have done a good job of eliminating the magenta hue with only a hint remaining.  There is also a process available (downloadable and installable script) for reducing magenta star colouring (often arises with NB colour combinations) - it uses a PixelMath formula.  Google 'Magenta Star Reduction.xpsm' and I'm sure you'll find it.  Alternatively, you can create a star mask, apply it and then use Colour Saturation to reduce the star colour saturation (can do the same with curves, reducing both hue and saturation).

Barry

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Barry: Thanks for the info regarding 'magenta star reduction'. Looks like I need one more iteration before I put this target to bed!

A.G: Good point. This is where art and science converge and why I find this hobby so rewarding!

Regards

John

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Thanks, Mick. I googled that last night. I appreciate that there's more to HST that just the standard SII->R, Ha->G and OIII->B mapping. Using PixelMath in PI can achieve a similar affect but it's far easier using Selective Colour in PS and moving sliders around  :smiley:

Regards

John

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It strikes me as odd to use HLVG or SCNR Green in a narrowband image because the green channel is not green at all, or probably isn't. It has been colour mapped. Change the colour mapping and the green channel might really be blue or red or whatever. Why would the green channel, irrespective of what filter's data went into it, always be noisy? It wouldn't.

Surely it would be more logical to get the noise under control in each channel and then weight the channels to give you the colour you want. Personally I don't like green in NB images (and rarely in broadband because it's usually, but not always, wrong) so I'd use Curves to bring down the green and bring up the others. You can do this directly in Curves or in the various Ps (etc) tools which manipulate the curve in clever ways. (Selective Colour, Colour Balance, etc etc.)

Personally I really like Komet's colour balance - but that really is a personal thing and no more than that.

Cracking capture, anyway.

Olly

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