In astronomy, the term "diurnal motion" refers to the movement of stars around the Earth's celestial poles due to the planet's rotation on its axis. This movement is called a diurnal circle.
Throughout the course of a day, the stars appear to move in an arc from east to west. From the North Pole, the stars appear to move in a counterclockwise motion. When viewed from the South Pole, however, they move in a clockwise motion. Scientists photograph examples of diurnal motion by taking long-exposure photographs of the stars throughout the night. The diurnal path by which a star moves is determined by its declination.