Photo
The Flame and the Horsehead Nebulae are emission nebulae in the constellation Orion and part of the Orion Molecular Cloud Complex which dominates this region of the winter night sky. Emission nebulae emit light as the result of the ultraviolet radiation of the nearby stars causing the elemental gases of the cloud to glow in much the same way as a neon or fluorescent light works. The variance in the colors between the Horsehead's pinkish red and the Flame's more orangeish pink is the natural result of the slight variations in the molecular makeup between the two clouds. The colors are naturally occurring and have not been manipulated by the photographer. In fact, if you were able to observe these nebulae through a telescope, you would likely see no color at all, as the human eye is not sensitive enough to detect color at the extremely faint levels that these nebulae present themselves. The bright star at the intersection of the two nebulae is Alnitak. This star would be the left-most star in Orion's belt as you view the constellation in the night sky.
To create this photograph, I attached a modified Canon XSi (450D) DSLR to my Sky-Watcher 120 mm refractor telescope. The camera has been modified by removing the infrared cut filter from the optical train, and replacing it with a narrow band IR pass filter which increases the camera's sensitivity the near infrared wavelengths that emission nebulae glow at. The telescope, with a focal length of 900 mm, is mounted to a Celestron CGEM german equatorial mount which has been polar aligned and is driven in synch with (and opposite to) the rotation of the earth to cancel out the stars' apparent movement across the night sky over the long exposure times necessary to capture the image. Once aligned, aimed and focused, I took a series of 30 individual photos, 90 seconds per frame at 1600 ISO. The shutter aperture is fixed at f/7.5 and is simply the ratio of the telescope's focal length (900mm) to its aperture (120mm). Additional dark frames were shot and the resulting images were combined in a process called 'stacking' using a special program (Deep Sky Stacker) written specifically for this type of astrophotography. The resulting image is then further processed using Photoshop and Noise Ninja to bring out the faint details of the subject and to reduce the level of sensor noise common to this type of photography.
Thank you for looking.
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