A catalogue of nearly five hundred celestial objects, published by Per Collinder as an appendix to his 1931 paper On structural properties of open galactic clusters and their spatial distribution. The catalogue is primarily dedicated to listing open clusters, groups of stars within the galactic disc that share a common origin and remain bound together by gravitational forces.
Objects within the catalogue are given numbers in the form 'Collinder 42' (an example that refers to the Pleiades in Taurus). Though the full name 'Collinder' is preferred in references, the abbreviation 'Cr' remains relatively common, and the rarer short form 'Col' is also occasionally seen.
The full Collinder Catalogue lists a total of 471 objects. Of these, 452 are recognised as belonging to actual open clusters, while the remaining nineteen are now considered to fall outside that classification. Of these other nineteen listed objects, eleven are globular clusters rather than open clusters, while several others are now seen as asterisms rather than true clusters (that is, groups of stars that merely appear to be clustered due to their line of sight from Earth). In a handful of cases (such as that of Collinder 269 in Musca), the status of the object still remains uncertain.
The selective list below summarises some of the better-known or most prominent clusters to be included within the Collinder Catalogue. For a fuller list, see the 'Collinder Catalogue' section of the Star Clusters index page.
Comparable in many ways to the Collinder Catalogue is the earlier index of star clusters known as the Melotte Catalogue. The Melotte list is more inclusive than the Collinder Catalogue, incorporating many globular clusters as well as open clusters, but it also rather less extensive, containing just 245 objects as compared with the Collinder Catalogue's 471. Both these catalogues include many of the brighterclusters in the sky, and so there is a considerable degree of overlap between the two systems. It is not uncommon, especially for more prominent clusters, to see both a Collinder number and a Melotte number referring to the same object. So, for example, as well as being listed as 'Collinder 42', the Pleiades are also designated 'Melotte 22'.