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Horsehead Nebula (also known as Barnard 33 in emission nebula IC 434) is a dark nebula in the constellation Orion. The image is a frame mosaic taken with 5 different filters, standard Red – Green – Blue with details enhanced with narrowband data of Hydrogen-alpha (Hα) and O III. The Hα was color-mapped to red and the O III to teal. So it is a representative color image consisting of over 900 minutes of exposure time.
© Ken Crawford Rancho Del Sol Observatory MPC G67
http://www.imagingdeepsky.com/Nebulae/Horsehead/Horsehead.htm