IC423 & IC424

Reflection Nebulas in Orion

Uploaded 1/6/06

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 This part of the sky is filled with wondrous objects, from dark unilluminated obscuring dark nebula to brilliant fluorescent colored emission nebulosities. Here we find a pair of very dim and strangely colored reflection nebula within a degree from an extremely brilliant 2nd magnitude star, Mintaka - AKA Delta Orionis. So obtrusive is this bright O9 star, that it makes imaging the

two faint nebula extremely difficult due to bright glare and reflections inside the optical system, and the huge number of geosynchronous satellites that run through this part of the sky. The small image here will enlarge to my original LRGB frame to show what I had to deal with in processing. The result of this effort is the larger image above, with most of the flares removed.

IC423 is the lower teardrop shaped nebula. The blue reflection nebulosity is mixed with the ultra dim core region colored with browns and reds from obscuring dust. Around the periphery of the core you can see a greenish tint from the mix of inner yellow and outer blues. IC423 is known also as LBN913, and is roughly 6 arcminutes in length.

Above is a strangely uniform blue patch of reflection nebulosity known as IC424. Covering 2.8 arcminutes of sky, it's serrated edges hint at invisible dust carving into its outline. Two 12th magnitude stars illuminate this nebula.

There is part of a larger emission nebulosity in the lower left corner, this part of Orion is filled with a luminous glow from red hydrogen.


Yes - and what an adventure this image was for sure. The techniques used for recovering this potentially disastrous image were performed in Photoshop CS2. First, satellite trails were removed by zooming in to view sub pixel resolution and piece by piece the trails were cloned out with adjacent blank sky as to not add any extra stars. The blue "rays" were harder. Since Mintaka is an O9 star, nearly all the rays were in the blue channel, and nearly none in the red. This good fortune made it a straightforward task to replace the sky in the selected regions with the red frames sky background, using a standard layer mask to apply this new background to only where the ray appeared. To remove the large number of blue rays that were over the nebulas themselves was the toughest part. The color of the rays was very close, but not exactly the same as the blue nebulosity, and the rays were very carefully selected with the color range command to exclude the nebula. Then they were darkened by pulling the mid tones down on the rays with curves so that it exactly matched the brightness of the nebula.

Instrument: 12.5" f/5 Home made Newtonian Platform: Astrophysics 1200 QMD CCD Camera: SBIG 10XME NABG with Enhanced Water Cooling Guider: SBIG ST4 Exposure: LRGB = 60:20:20:20 (RGB Binned 2x2) RGB Combine Ratio: 1: 1.05: 1.11 Filters: AstroDon RGB Tricolor Location: Payson, Arizona Elevation: 5150 ft. Sky: Seeing FWHM = 5.5 arcsec (Maxim DL - 10min subframe), Transparency 9/10 Outside Temperature: 31F CCD Temperature: -30 C Processing Tools: Maxim DL, Gralaks Sigma, Photoshop, PixInsight, CCDOps Debloomer. HOME GALAXIES EMISSION NEBS REFLECTION NEBS COMETS GLOBULARS OPEN CLUST PLANETARIES LINKS


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