David Dunlap Observatory Catalogue

David Dunlap Observatory Catalogue, known as the DDO or A Catalogue of Dwarf Galaxies, is a catalogue of dwarf galaxies that was compiled by Sidney van den Bergh and published by the David Dunlap Observatory in 1959 (and later expanded in 1966). Examples DDO 3 DDO 3 (also known as NGC 147, PGC 2004, UGC 326, LEDA 2004 or Caldwell 17) is a dwarf spheroidal galaxy which is located in the northern constellation of Cassiopeia, near the border of Andromeda. It is a small satellite galaxy of the famous Messier 31, which is the largest galaxy in the Local Group.