The Horsehead Nebula (also known as Barnard 33 in emission nebula IC 434)
is a dark nebula in the constellation Orion.
It is, in fact, an extremely dense cloud projecting in front of the ionized gas that provides the pink glow so nicely revealed in this picture.
We know this not only because the underside of the "neck" is especially dark, but because it actually casts a shadow on the field to its east (below the "muzzle").
The red or pinkish glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis.
The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left.
Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming. (WIKI)
Imaged with Boren-Simon 10" F/2.8 POWERNEWT Astrograph.
SBIG ST8300M camera with FW5 filterwheel and BAADER LRGB filters.
L = 120 minutes
RGB = 10 minutes each (BIN 2x2)
Total of 150 minutes.
NO HYDROGEN ALPHA!
Imaged from the NEGEV desert in ISRAEL