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Rod Pommier

Location of Photo:

Pommier Observatory, Portland, Oregon, USA

Date/Time of photo:

2012-10-06 through 2013-10-10


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. Exposures: H-alpha:R:G:B=420:80:80:80=11 hours total exposure.


The Horsehead is backlit by the emission nebula IC 434, which glows by ionization from the nearby hot blue star Sigma Orionis. Solar Winds from it are pushing the nebula outward causing both the striations and the billowing shock front where it is being compressed against the dark molecular cloud, of which the Horsehead is a persistent protrusion wherein new stars are forming. 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 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.


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