Each image is described by it catalogue identification. Most are named after an astronomer who identified and catalogued the target. Some targets are found in more than one catalogue. Below are the most common:

• • Caldwell (list compiled by Sir Patrick Moore)
  • IC (The Index Catalog)
  • M or Messier (list compiled by Charles Messier)
  • NGC (New General Catalog)
  • SH (list Compiled by Stewart Sharpless)
  • VdB or VDB (compiled by Sidney van den Bergh)