Alnitak Region

B33 (Horsehead Nebula), NGC 2024 (Flame Nebula), NGC 2023, IC 431, IC 432, IC 434 and IC 435 in Orion

LRGB combination (Click for a larger view 1800 x 1800 px)


Click for wallpaper suitable images: 1440 x 900 px and 1280 x 1024 px


B & W version (mix from 45% green and 55% red channels) (Click for a larger view 1800 x 1800 px)


B33 (Horsehead Nebula), NGC 2024 (Flame Nebula), NGC 2023, IC 431, IC 432, IC 434 and IC 435 in Orion

The Horsehead Nebula is one of the most famous nebulae, about 1600 light years away, in the constellation of Orion. The horse head feature is actually a dark nebula, of opaque dust, also cataloged as Barnard 33 or B33. Just to the south of Alnitak (Zeta Ori), this region is dominated by the background emission nebula known as IC 434. The emission nebula's red color is caused by electrons recombining with protons to form hydrogen atoms. Barnard 33 (B 33) is thought to be part of the underlying dust cloud that forms the dark lanes in the Flame Nebula.

NGC 2024 (Flame Nebula) one of the most remarkable reflection nebulae in the night sky, has an underlay of glowing Ha (red) emission but is strongly overlaid with reflected light from Alnitak resulting in almost unique and beautiful colours, ranging from shell-pink through yellow to deep orange. Additional dark gas and dust lies in front of the bright part of the nebula and this is what causes the dark network that appears in the center of the glowing gas.

NGC 2023 - This bright complex of dust and gas is located near the famous Horsehead Nebula, slightly below the left. It reflects the light given off by the bright star near it's center and is one of the brightest examples of reflection nebulae in the northern sky. The central star is surrounded with a thin shell of hydrogen that glows red by emitting its own light in a rare example of a unique process called vibrational fluorescence. There are also a dark clumps of gas that represent stellar nurseries containing one or more new stars hidden within. NGC 2023 nebula lies approximately 1 600 light years from earth.

Other reflection nebulae in the photo are IC 435, IC 434, IC 432 and IC 431

List and crossreference:

B33 (Barnard 33) - Horse Head Nebula
NGC 2024 (CED 55P, Flame Nebula) - Bright Emission Nebula
NGC 2023 (LBN 954) - Bright Reflection and Emission Nebula
IC 434 (LBN 953, Sh2-277) - Emission Nebula
IC 431 (LBN 944) - Bright Reflection Nebula
IC 432 (LBN 946) - Bright Reflection Nebula
IC 435 (VdB 57) - Bright Reflection Nebula

The Horizontal FOV is about 110'. The image almost centered at:

Right Ascension 05 : 41.5 (h:m)
Declination -02 : 02 (deg:m)
Distance 1.6 (kly)
Brightness 7.2
Apparent Dimension

B33 - 6 x 4 (arc min)

NGC 2024 - 30 x 30 (arc min)

Seeing: Pickering 7 rating - Good
Optic(s): APO 90/600+WO field flatener @ f/4.9
Mount: CGE equatorial
Camera: Artemis Art 4021 - monochrome cooled CCD camera – 2048 x 2048 px ; 16x16 mm; 7.4 µm x 7.4 µm
Filters: L, R, G, B set Astronomik II, SupaSlim Truetek Computerized Filter Wheel
Dates/Times: 2011-11-04
Location: Rozhen Observatory, BG, longitude: E 24 44' 18", latitude: N 41 41' 42"
Exposure Details:

L= 20 min, R = 50 min, G = 60 min, B = 50 min, (Bin1), Subexposures: LRGB = 10 min, Total Exposure Time - 180 min

More details: Dark frames reduction
Guiding: Starlight Xpress Lodestar Autoguider on Celestron 11" Schmidt Cassegrain

PixInsight / PS


All Contents copyright Velimir Popov unless otherwise noted.