The Horsehead & Flame Nebula
(Click on Pictures for larger view)

The Horsehead Nebula
The 'Horsehead' / 'Flame' Nebula is about 1,375 light-years away and the horse's head is mainly a large cloud of interstellar dust obscuring the stars and nebulous gasses. The red color originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis above the horse's head. There is an additional abundance of hydrogen dust throughout this region which glows in a red color caused by the radiation of nearby stars.

Image taken with a One-Shot-Color Camera using a special light pollution filter sensative to the red and blue light only I took this image using a monochrome camera using narrowband filters, however, the Oxygen3 4nm filter (which I usually use for the blue color) was rejected as it didn't handle the blue light from the bright star Alnitak so I used the Luminance (UV/IR) filter instead for the blue.

Equipment:

Telescope: Orion ED80 Triplet Refractor
Reducer: Orion 0.8x for short focal length refractors
Focal length: 384mm
Focal ratio: f/4.8
Camera: ZWO ASI 071 mc Pro ...One-Shot-Color
Filter: Optolong L-eNhance
Subframes: 53 x 300 sec
Total integration time: 4hr:25mn
Camera Gain ... sensor temp: 139 ... -10°C
Mount: Celestron AVX
Capture Software: N.I.N.A. Beta 2.015 nightly build
Guiding: PHD2
Stacking: Deep SkyStacker
Post-processing: PixInsight, Photoshop CC, and TOPAZ DeNoiseAI

That "Techy" Stuff
Telescope: Orion EON 130mm Triplet Refractor
Field Reducer: Orion 0.8x for the EON
Mount: SkyWatcher EQ6-R Pro
Camera: ZWO ASI 1600mm Pro ... Monochrome
Filters: - Hydrogen-Alpha (3,5nm) ... Sulfur2 (6nm) ... UV/IR Cut
Subframes: 20 x 180 sec Ha & S2 ... 30 x 60sec Uv/IR
Total integration time: 2hr:15mn
Camera Gain ... sensor temp: 139 at -10°C
Capture Software: N.I.N.A. Beta 2.007 nightly build
Guiding: PHD2
Stacking: Deep SkyStacker
Color combination:
Red: a 50/50 blend of the Sulfur2 and Hydrogen Alpha
Green: Hydrogen Alpha
Blue: Luminance (UV/IR)
Post-processing: PixInsight, Photoshop CC, and TOPAZ DeNoiseAI

Getting Color from Black & White

The color in the narrowband image comes from combining the different black & white images in the 3 main color channels of red-green-blue within the image composition.
RED portion of the image ... I use a 50/50 blend of the hydrogen-alpha and the sulfur 2 images.

GREEN portion of the image ... I used the hydrogen alpha image.

BLUE portion of the image ... I usually would use the oxygen 3 image, but there was a flaw in that spectrum ... see the 'square' star. So I used the luminance image for the blue instead.

You can see more by watching my video as to how I made these images: What Makes the Horsehead Nebula Glow?

The nebulosity of this area is caused mostly by emission of red light from the radiation from nearby massive stars, particularly Alnitek (just above the 'Flame' and the double blue star Sigma Orionis (above and to the upper right of the horse's head. These two stars are extremely young and extremely hot ... 29,000-31,000°K as compared to our sun which is burning at a steady 5,775°K. These stars are only a few million year old, as compared to the age of the sun at 4.6 billion years.

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