Star Trails Above Soelden, Austria
December 20, 2007
This photo showing a series of star trails across the night sky was taken over Soelden, Austria on February 4, 2007. The fact that the celestial sphere is rotating (or more accurately, of course, that the Earth is) can be seen when observing long-term exposures of the sky. In particular, close to the celestial equator the rather dramatic traces of stars, like this one, give an impression of the apparent motion of the celestial sphere. Nearly three hours of observing were required to capture this image of the sky above the Soelden ski resort (2,700 m or 8,858 ft) in western Austria. The effect comes about as the celestial equator, a plane dividing the celestial sphere into a northern half and a southern half, passes through the constellation of Orion, which is seen here in the lower center of the picture.