Author Topic: Helix nebula in bi-colour NB with RGB stars  (Read 3983 times)

Offline RickS

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Helix nebula in bi-colour NB with RGB stars
« on: 2013 December 18 04:53:02 »
I had lots of fun playing with this image and discovered a bunch of new tricks and techniques.  A few of them even worked as expected  :D


Offline NGC7789

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Re: Helix nebula in bi-colour NB with RGB stars
« Reply #1 on: 2013 December 18 06:04:56 »
This is really nice! Any chance you can share some of those tricks and techniques? What was your workflow?

Offline RickS

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Re: Helix nebula in bi-colour NB with RGB stars
« Reply #2 on: 2013 December 18 13:20:55 »
This is really nice! Any chance you can share some of those tricks and techniques? What was your workflow?

Thanks!  Probably the neatest trick was a new way (for me, at least) of merging the RGB stars into the narrowband image.  Here are my processing notes.

Quote
NGC 7293 (Helix Nebula)

Narrowband taken at St Lucia, August/September, 2013
LRGB taken at Glen Aplin, 6-7 September, 2013

Objects in image:
  NGC7293

Scope: Ceravolo C300 @ f/9 = 2760mm FL, Atlas focuser
Mount: AP900
Camera: U16M
Filters: Astrodon E series Gen 2 LRGB
Guiding: Lodestar / MMOAG
Image scale: 0.67 arcsec/pixel
Exposures: 43x1800s Ha, 43x1800s O3, 4x1800s S2, 5x900s R/G/B, 8x600s Lum (43 hours NB, 5 hours LRGB)

Conditions:
- Various

Processing...

Notes:
- Star mask subtraction from luminance: "iif(star_mask>0.2,min($T,0.8-star_mask),$T)" then blur (remove wavelet 1..4)
- Cyan mask: iif((CIEa($T)<0.5)&&(abs(CIEa($T)-CIEb($T))<0.3),1,0)
- Pink mask: iif(CIEa($T)>0.53&&CIEa($T)<0.75&&CIEb($T)>0.53&&CIEb($T)<0.75,CIEL($T),0)

Pixinsight:
- BPP calibration with overscan, CosCorrect
- Register against "nI NGC 7293-S001-R001-C001-Ha.fts"
- Integrate all for best SNR
- Crop all
- DBE all

RGB stars:
- Decon to match RGB star sizes
- LRGBCombine
- Unlinked stretch
- mask & saturate stars
- mask & ATWT blur stars
- Curves H to reduce cyan

Ha:
- light decon
- DBE
- light masked MMT nr
- stretch

O3:
- light decon
- DBE
- light masked MMT nr
- stretch

NB:
- LRGBCombine: L=Ha, R=Ha, G=O3, B=O3
- Masked (Lum-stars) HDRMT 6 layers, LHE 0.5
- Masked (Lum-stars) HDRMT 7 layers
- Masked (Lum-stars) HDRMT 8 layers
- Blend all 1:1 with original
- Rangemask background and desaturate, heavy TGVDenoise
- Rangemask dim nebulosity and stretch
- Overall masked TGVDenoise
- Tweak black point
- Curves H: green centre -> bluer
- ColourSat: blue
- ICCProfileTrans -> ProPhotoRGB
- Build masks for major colour areas (PixelMath using CIEa/CIEb)
- Tweak colours with CIE a and b curves
- reduce stars1:
    - Extract Lum, Big HDRMT, Starmask big, starmask small, iif(small>0.25,0,big) -> ring mask,
      MT selection, HT stretch, apply & MT selection
- reduce stars2:
    - Starmask + MT
- Create star mask from NB luminance * strong HDRMT
- Extract CIE L*a*b*
- PixelMath a*: iif(RGB_star_mask>0.1,RGB_star_mask*CIEa(RGB_stars)+(1-RGB_star_mask)*$T,$T)
- PixelMath b*: iif(RGB_star_mask>0.1,RGB_star_mask*CIEb(RGB_stars)+(1-RGB_star_mask)*$T,$T)
- Repeat a couple of times
- Recombine L*a*b* [PixelMath copy over clone of original - why needed???]
- Masked slight ATWT sharpen layers 1-3, 6-8 (mask for Lum & star protection)
- Tiny stretch
- Voila!



Offline Geoff

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Re: Helix nebula in bi-colour NB with RGB stars
« Reply #3 on: 2013 December 18 14:13:52 »
Stunning image Rick. One of the best shots of the Helix I've ever seen--APOD material.
Geoff
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Offline Jan

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Re: Helix nebula in bi-colour NB with RGB stars
« Reply #4 on: 2013 December 18 14:27:26 »
Very nice work, nothing to add:-) Congrats and looking forward to see more pictures!

Offline marekc

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Re: Helix nebula in bi-colour NB with RGB stars
« Reply #5 on: 2013 December 18 15:09:27 »
Another nice example of narrowband nebulosity with good-looking RGB stars!

There have been a lot of nice images of this type on the PI Forum lately, and it's a lot of fun to send people kudos! I think this is another very good example of putting RGB stars into the image, and the deep nebulosity is really impressive.

- Marek

Offline RickS

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Re: Helix nebula in bi-colour NB with RGB stars
« Reply #6 on: 2013 December 19 01:51:10 »
Thanks Geoff, Jan & Marek!

Offline dayers

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Re: Helix nebula in bi-colour NB with RGB stars
« Reply #7 on: 2013 December 19 06:06:40 »
Thanks for sharing your workflow, Rick. This sounds like it was quite a project, and the result is by far the best rendition of the Helix that I have seen.

Dave
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Offline Lex

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Re: Helix nebula in bi-colour NB with RGB stars
« Reply #8 on: 2013 December 19 14:36:00 »
APOD +1!!!!!
Clear Skies!!

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Offline RickS

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Re: Helix nebula in bi-colour NB with RGB stars
« Reply #9 on: 2013 December 20 00:08:41 »
Thanks Dave & Lex  :D