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Yet another M42...


Hallingskies

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Not that anyone could get fed up with this object...

M42-6.jpg

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 AstroArt4, then composited in Paint Shop Pro7.

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.

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 (though you can “weight” colours to compensate for CCD sensitivity at different wavelengths), 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 four stars shines brilliantly 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.

Any comments, criticisms or suggestions gratefully received...

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