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star trail

n. (context astronomy photography English) The line of light recorded on a photographic medium when a time exposure is made of a star in the nighttime sky using a camera on a fixed mount, caused by the rotation of the earth during the period of time when the camera's shutter is held open.

Wikipedia
Star trail

A star trail is a type of photograph that utilizes long-exposure times to capture the apparent motion of stars in the night sky due to the rotation of the Earth. A star trail photograph shows individual stars as streaks across the image, with longer exposures resulting in longer streaks. Typical exposure times for a star trail range from 15 minutes to several hours, requiring a 'bulb' setting on the camera to open the shutter for a longer period than is normal.

Star trails have been used by professional astronomers to measure the quality of observing locations for major telescopes.