Exposure: 6x300" @ ISO 800 (RGB) + 11x900" @ ISO 800 (Ha)
Telescope: William Optics Megrez 88FD with Baader MPCC
Filter: Hutech IDAS LPS 2" (RGB exposures) and Baader H-alpha 7nm 2" (Ha exposures)
Mount: Meade LXD-75 Autostar
Camera: Modded Canon 350D
Date: November 2008
Location: Cabrera de Mar (suburban site near Barcelona) (Ha) and El Montseny (RGB)
Comments: This was my first combined Ha+RGB image. I used a cross mask for focusing Ha exposures and I forgot to remove it in the light exposures, that's why the stars have these weird spikes. The RGB exposures were a bit foggy because of strong high clouds in the sky, that's why the halos of the stars are that prominent.
This nebular complex around Alnitak (zeta orionis), the brightest star of the field and one of the three members of the Orion's belt, is formed mainly by the Flame nebula (NGC2024), below Alnitak, IC434 on which there is B33, the popular Horsehead nebula, is to the right of Alnitak. It is approximately 1500 light-years from the Earth.
The red glow is originated 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. 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.