Flame Nebula - Blog Posts
The Horsehead Nebula (Barnard 33, below center) and the Flame Nebula (NGC 2024, below left of center) // AstroFortWayne
The glow of ionized hydrogen in the Flame Nebula, in Orions belt, by Adam Block
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Ok, so I was searching for information on some of the objects visible in my photo of the horse head nebula and I found these two posts (Reddit and Astrobin) by DanielZoliro that also used a SII and Ha combination but with a slightly different processing (Notably, the RGB combination being R: SII, G: 0.6xHa + 0.4xSII, B: Ha). I loved his results and I had to try it with my own data. Did turn out great, but there was a reflection of a star on the SII data and this processing amplified it (the big reddish round/donut thing on right of the full image).
(Image taken using a CarbonStar 150/600 newtonian telescope with a 0.95 coma corrector, ZWO ASI294 monochrome camera and Baader 6.5nm SHO filter. 5x120s image for each colour filter (RGB), 22x300s for the Ha filter and 32x300s for the SII filter, total imaging time 5h, stacking and processing done in PixInsight.)
Finished working on my photo of the hors head.
Technically speaking the Horse Head is only the dark nebula, is bright hydrogen cloud behind it is known as IC434 and the second nebula (bottom left) is the flame nebula. The bright star in the center left is Zeta Orionis also known as Alnitak one of the three stars of Orion's Belt. IC434 primary ionisation source is the multiple star system Sigma Orionis (a bit above the frame), the hydrogen cloud being mostly ionise by the UV coming from those blue giant stars. The streaks visible in the nebulosity are mostly likely due to magnetic field within.
The Flame nebula's ionisation source is hidden behind it's dust cloud and is most likely part of a star cluster that Is only reviled using IR and X-ray imaging.
This photo appears mostly blue/teal wear-as most photos of this nebula are red(ish) this is because this nebula emits most of it's light in the H-alpha (656 nm) and S-II (around 672 nm) wavelength both of which are red, so in classic RGB images the nebula appears red. Initially I thought of doing an SHO image (were red is SII emission, green is H-alpha and blue is OIII) but this nebula lacks OIII emission (around 500 nm), so instead a used a modified SHH palette More precisely, I used SII for the red, a combination of both Ha and SII (0.8Ha + 0.2SII) for green and Ha for blue. The stars were taken separately in RGB and added back to the SHH image.
(Image taken using a CarbonStar 150/600 newtonian telescope with a 0.95 coma corrector, ZWO ASI294 monochrome camera and Baader 6.5nm SHO filter. 5x120s image for each colour filter (RGB), 22x300s for the Ha filter and 32x300s for the SII filter, total imaging time 5h, stacking and processing done in PixInsight.)