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.