Catalogue of designations

This catalogue (table a101 in the database) is the compilation of designations of objects. In general, the designations are formed from an acronym of the catalogue where the source is described followed by a running number: For example, NGC 4486 means "the object number 4486 in the New General Catalogue". A given object may have several names.

The designations should comply rules defined by the commission 5 of the IAU, and new acronyms should be declared to this commission. There are some variants between the coding of names between the various databases, Simbad and NED in particular. HyperLeda tries to use names as widely accepted as possible.

For most of the recent large surveys, the names are build from the acronym and from the position of the object on the sky (in general the J2000 equatorial coordinates). Note that the position must be "truncated" not "rounded".

Galaxies and nebulae names

Historically, galaxies and nebulae were not distinguished. Both type of objects appear extended and diffuse at the telescope, and this is not until the 20th century that the nature of galaxies ware recognized. Catalogues assembled by searching the sky with a telescope or on photographic or digital surveys therefore often include both galaxies and gazeous nebulae, because a precise classification sometime needs additional data (like for example a spectrum, or images taken at different wavelengths). The next table gives some of the best known catalogues of galaxies or of nebulae.