The Diurnal motion reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Diurnal motion

Diurnal motion is an astronomical term referring to the apparent daily motion of stars in "orbit" around the Earth, caused by the Earth's 24-hour rotation about its axis.

Such motion can be seen in time-exposure photography. Some of the more circumpolar stars close to the celestial pole may appear to be relatively motionless.

See also: celestial sphere positional astronomy

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