M42 - The Great Orion Nebula...

Object: Messier 42 (NGC 1976)
Type: Emission Nebula
Constellation: Orion
Distance: 1340 light years

Date: 01 January 2018
Equipment: SXV-H9, Vixen 114mm f5.3 ED refractor, guiding with Lodestar X2/PHD

Subframes: 30 x 300s, 100s & 20s H-alpha, 20 x 20s & 100s RGB 2x2 binned, 20 flats for each channel, no darks (hot pixel removal in Astroart instead).

Images were acquired and pre-processed (aligned, stacked, denoised) in AstroArt, then composited in Paint Shop Pro.

The Orion Nebula presents quite a challenge to depict because of the wide brightness range of its key features. Many early CCD images of this object as shown on the web "burn out" the "trapezium" region of the four central stars in attempting to show the outlying nebulosity.

I use the "layers" function in PaintShop Pro, stacking the longest exposures on top of shorter ones, and then carefully use the "eraser" tool to remove overexposed areas, leaving the underlying correctly exposed regions to show through.  This has to be done with care to avoid introducing obvious processing artefacts.

The luminance (H-alpha) channel, processed as described above, is shown below:

Whilst the latest image processing programs such as Pixinsight have "dynamic range adjustment" features that can automatically produce an even distribution of brightness, some of the resultant images can seem rather strange to my eyes.  Programmes like that are way beyond both my budget and my understanding!

LRGB combination (using the H-alpha stack as the luminance channel) went well in both Astroart and PaintShop Pro. The PSP version was a lot greener than the Astroart one (which automatically weights colours given that most CCDs are more sensitive to green light than red or blue, I guess), but I preferred the PSP output as it hinted at the greenish hue of the nebula that is so clearly discernible though the eyepiece.

All of the brighter features seen in the above image show clearly through my VC200L and a 25mm eyepiece. The central trapezium of the four stars brilliantly shine against a bright silvery background, which fades into the convoluted greenish wings of the surrounding nebula.  The dark channel between the main portion of the nebula and the upper candle-flame is clearly seen.

I strove to retain all of these key features in the image above, as well as highlight the extended nebulosity that the eye cannot see.

More information about this object can be found here.