Alternatively, an astronomical survey may comprise a set of images, spectra, or other observations of objects that share a common type or feature.
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.
The wide scope of surveys makes them ideal for finding foreground objects that move, such as asteroids and comets.
Similarly, images of the same object taken by different surveys can be compared to detect transient astronomical events such as variable stars.