ESO = The ESO/Uppsala Survey of the ESO(B) Atlas by Lauberts [27]

GC = General Catalogue by Herschel 1864 [17]

IC = Index Catalogue of Dreyer [12]

M = Messier's (1784) catalogue of nebular objects [34] , modern version [16]

MOL = Master List of Non-Stellar Astronomical Objects by Dixon and Sonneborn [10]

NGC = New General Catalogue by Dreyer [11]

RNGC = Revised New General Catalogue by Sulentic and Tifft [44]

Of 110 entries in Messier's catalogue, the 39 objects listed below are now known to be external galaxies (see [16] for a modern and accessible compilation). A similarly large proportion of the entries of GC, NGC, and IC are also extragalactic as evidenced by the early examination of the GC [222], and subsequent modern re-examinations RNGC [44]. This latter study is based upon an inspection of the objects as they appear on the POSS-photographs [53] and so descriptions are limited to northern objects.

Only as the true nature of the various classes of ``nebulae'' became known in the early decades of the twentieth century, did external galaxies lay claim to being catalogued in their own right. Nevertheless, in the tradition of the NGC, the ``Quick Blue'' European Southern Observatory (ESO) Sky Survey was made available with extensive listing and descriptions of all non-stellar southern objects [18, 27] so as to make interesting new Galactic and extragalactic objects immediately available to the large reflectors being completed in the southern hemisphere.

Collectively, the compilations cited above contain most of the apparently brightest galaxies in the northern and southern hemispheres in their files. Prior to this the most comprehensive compilation of non-stellar objects drawn from the published literature, and merged purely by a sequential positional ordering, is the Master List of Non-Stellar Astronomical Objects by Dixon and Sonneborn [10] which contains a listing of over 200,000 entries. Recently the NGC/IC catalogues have been been made more accessible in a corrected form, updated to the equinox 2000.0 [43]