Celestial hemisphere:  Northern  ·  Constellation: Cassiopeia (Cas)  ·  Contains:  IC 1590  ·  NGC 281
NGC-281, The Pac-Man Nebula, in Ha/OIII and RGB stars, fewayne
NGC-281, The Pac-Man Nebula, in Ha/OIII and RGB stars
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NGC-281, The Pac-Man Nebula, in Ha/OIII and RGB stars

NGC-281, The Pac-Man Nebula, in Ha/OIII and RGB stars, fewayne
NGC-281, The Pac-Man Nebula, in Ha/OIII and RGB stars
Powered byPixInsight

NGC-281, The Pac-Man Nebula, in Ha/OIII and RGB stars

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Description

The "Pac-Man" nebula appears here in bicolor (H-alpha red, O-III blue and green), together with a composited image of the stars in RGB.

I was surprised to see how much star color could be obtained with very little effort, this is just 20x30" each of R, G, and B at 65 gain.

I think if I redo this, I will remove the Starnet step entirely. I really didn't do any further stretching or enhancement of the nebulosity that I couldn't have accomplished by just masking in Photoshop, and I got tired of fixing all the halo artifacts around the stars long before I ran out of artifacts. A few notes on the processing:

-- I leaned heavily on Astro Pixel Processor's light-pollution/gradient reduction tool, processing the individual H-alpha and O-III integrations with well over a hundred sample boxes drawn on each. After compositing, I ran the combined image back through it again.

-- Since, as always, the O-III data were so much weaker, I had to multiply them pretty hard in the combine tool, about 6 or 7X, while the H-alpha were pulled down to about 0.8X. That had the effect of stretching the color data pretty hard, so I wound up using Topaz Denoise AI on the nebulosity pretty hard too, then Sharpen AI on the result to regain some of the lost detail.

-- The separate RGB stars image was also run through LPR twice, first as individual channels and then as a composite. I adjusted the star color to better fit the H-R trendline in APP's star calibration tool. In Photoshop, I used a Levels tool to set the background to black and eliminate most the faint trace of H-alpha nebulosity that came through. One of the last steps on the final composite image was a Photoshop Minimum filter to eliminate some of the smaller stars.

Comments

Revisions

  • NGC-281, The Pac-Man Nebula, in Ha/OIII and RGB stars, fewayne
    Original
  • NGC-281, The Pac-Man Nebula, in Ha/OIII and RGB stars, fewayne
    B
  • Final
    NGC-281, The Pac-Man Nebula, in Ha/OIII and RGB stars, fewayne
    C

B

Description: This is just a full-res version so the pixel scale is correct.

Uploaded: ...

C

Description: Adjusted the black point for more pleasing contrast. Used Gaussian Blur like a sledgehammer on the background of the starless image to get rid of the awful halo artifacts. Lost some faint traces of nebulosity in the background, but a good trade.

Uploaded: ...

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NGC-281, The Pac-Man Nebula, in Ha/OIII and RGB stars, fewayne