by Rod Pommier
Telescope/Mount: Celestron Compustar C14 with Astrophysics 0.75x focal reducer (f/8.3).
Camera: SBIG STL 11000M with Baader Planetarium H-alpha, R, G, and B filters.
Location: Pommier Observatory, Portland, OR, USA.
Dates: 2013-10-06 through 2013-10-10.
Exposures: H-alpha:R:G:B=420:80:80:80=11 hours total exposure.
The elusive Horsehead Nebula, Barnard 33, is a dark nebula in Orion. It is just south of Alnitak, the eastern star in Orion's belt.The Horsehead is back lit by the emission nebula IC 434,
which glows due to ionization from the nearby hot blue star Sigma Orionis. Solar winds from
Sigma Orionis are pushing the emission nebula outward causing both the striations in the nebula and the billowing shock front where the emission
nebula is being compressed against a dark molecular cloud, of which the Horsehead is a persistant protrusion. Newborn stars are forming within the Horsehead. While it is one of the most iconic nebulae in astronomy, the Horsehead is elusive to photograph and display with image processing because the regions of the base of the horse's neck are only 0.02% brighter than the the average background sky values. Despite these feeble differences, the neck of the Horsehead Nebula can actually be seen to cast a shadow to the lower left across that region. Other examples of light and shadow can also be seen. The Horsehead Nebula lies approximately 1500 light-years from Earth.