survey field

The phrase survey field (or survey region or sometimes field of view or FOV) is used for the portion of the celestial sphere where an astronomical survey's observations are carried out. The phrase all sky survey means just that, but is also used to indicate a substantial fraction of the sky, e.g., for survey performed from a single ground location, all that is reachable. Surveys often reuse a past survey field to carry out additional observations, e.g., covering other parts of the electromagnetic spectrum, greater depth, or adding spectrography. A deep field is a (generally small) field used for extreme depth, i.e., looking for distant and therefore faint objects. The term wide field is sometimes used for a large survey field, but also is used to indicate a large field of view.

Survey fields are often re-used, i.e., a subsequent survey is intended to gather more data on the field's known objects (and to search for more), and for the same reasons, sometimes a new survey field is specifically chosen to overlap with an existing field. These are especially true of deep fields.