rare designator prefixes

These are a number of prefixes used in designators of astronomical objects (e.g., stars or galaxies) that are not commonly seen for large numbers of objects. An IAU initiative offers formalized designation formats with the aim of object-references that are and remain unique and traceable, but designator prefixes actually used for objects are ultimately chosen by those who write or talk about the objects, and they often choose something convenient to write and say, often shortening the prefix. Such seldom-used designator prefixes include:

• prefixes from old catalogs, kept in circulation through continued interest in one or a few objects. It might be a designator specific to the catalog, or it might be, or include, an indicator of the discoverer.
• prefixes for some object in such an old catalog if interest in the object has been revived, such as when an extra-solar planet is discovered around a star which has long been rather ordinary as far as research is concerned.
• prefixes coined in a more recent paper based on the object's discoverer or institution or observatory.
• prefixes used for any of the many compiled lists of objects in papers, which range from thousands of objects down to tens or fewer, often too short to call a "catalog". The prefix may have been coined by compiler of the list, or by a subsequent researcher who is referencing an object in the list.

See also double star designation as well as the full index of Survey/Catalog identifiers.