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Astronomical survey

General map or image of a region of the sky with no specific observational target

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Through Sky and Electromagnetic spectrum

Surveys have generally been performed as part of the production of an astronomical catalog. They may also search for transient astronomical events. They often use wide-field astrographs.

Scientific value

Sky surveys, unlike targeted observation of a specific object, allow astronomers to catalog celestial objects and perform statistical analyses on them without complex corrections for selection effects. In some cases, an astronomer interested in a particular object will find that survey images are sufficient to make new telescope time entirely unnecessary.

Surveys also help astronomers choose targets for closer study using larger, more powerful telescopes. If previous observations support a hypothesis, a telescope scheduling committee is more likely to approve new, more detailed observations to test it.

The wide scope of surveys makes them ideal for finding foreground objects that move, such as asteroids and comets. An astronomer can compare existing survey images to current observations to identify changes; this task can even be performed automatically using image analysis software.

Besides science, these surveys also detect potentially hazardous objects, providing a service to Spaceguard. For example, the Asteroid Terrestrial-impact Last Alert System (ATLAS) system surveys the entire night sky every night and, like NEOSTEL, is intended to detect objects as they approach. Broader surveys include the Uppsala–DLR Asteroid Survey and the 20th-century U.K. Schmidt–Caltech Asteroid Survey. Old surveys can be reviewed to find precovery images.

Similarly, images of the same object taken by different surveys can be compared to detect transient astronomical events such as variable stars.

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