Orion Rising Over Death Valley

The constellation Orion over a tent - Death Valley National Park, California
The constellation Orion over a tent - Death Valley National Park, California

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My wife and I were camping on a rise overlooking Death Valley near Warm Spring Canyon road when I took this photo. The waning moon, a couple of days past full, had risen a few hours before, and was illuminating veils of cloud which were drifting overhead.

The constellation Orion, the hunter, is located in the top-center of the photo. His shoulders are the top two bright stars. The two lines of three stars compose his belt and sword. Orion includes two of the brightest stars in the sky: the blue giant Rigel, and the red supergiant Betelgeuse.

Figure showing location in the photograph of Orion, Rigel, Betelgeuse, and Belt & Sword.

The sky appears blue for the same reason that it appears blue during the day — preferential scattering of short-wavelength blue light by the atmosphere, in this case moonlight as opposed to sunlight during the day. The night sky appears black to our naked eye only because the light is so dim. A long-exposure camera shot such as this (15 sec. at f/3.5, ISO 400) amplifies the light enough to see its true color.