Horsehead Nebula
ST-10XME C14 LRGB at F7.4 (Astrophysics focal reducer)
Luminance and colours binned 2x2 (1.1 arcsecond per pixel)
L=4x10 min.
R=G=B=10 min.
The well known dark nebula in Orion. The catalogue designation is B33.