The Catalog of Galaxies and Clusters of Galaxies
(aka Zwicky Catalog, and abbreviated CGCG or sometimes ZC)
is a list (in eight volumes, I to VIII) published by Fritz Zwicky
beginning in 1961, that totals more than 29000 galaxies and 9000
galaxy clusters identified in the Palomar Observatory Sky Survey (POSS)plates.
(The designators used for the catalog's galaxies
were atypical: they began with the volume number, e.g.,
"II Zw example II Zw 96" for the 96th galaxy in volume II:
these are now often reversed, i.e., "Zw II 96",
or "CGCG" is used with coordinates.)
Since publication, the catalog has been updated with
corrections and it remains in use for research,
such as selecting samples for study.
The Updated Zwicky Catalog (UZC) is a 1990s
update, using newer observations to correct data
and add precision.
The Catalogue of Selected Compact Galaxies and of Post-eruptive Galaxies
(CGPG) is Zwicky's 1971 list
of compact galaxies (smaller than typically-observed galaxies),
and post-eruptive galaxies (Zwicky's term for galaxies with
atypical spectral energy distributions and/or morphology, which perhaps included what is
now known to be characteristics of active galactic nuclei, AGNs, but I can't tell).
Zwicky selected many of these from his CGCG, cross-referencing
them with the CGCG designators, which are often used to refer
to this catalog's entries.