David Dunlap Observatory Catalog

The David Dunlap Observatory Catalog is a 1950s catalog of dwarf galaxies from observations at David Dunlap Observatory. The observatory is north of Toronto, Canada, and houses a 1.9-meter reflector telescope dating from 1935, which is currently used for education. The catalog introduced an enhanced galaxy type system that includes a luminosity class analogous to the existing stellar luminosity classes, each including a subsequent Roman numeral, I, II, etc. Note that as a galaxy luminosity class, V indicates a typical dwarf galaxy luminosity. The term DDO classification refers to this Roman-numerical classification system, or to a specific galaxy's classification as given by the catalog.