Deep space object

Deep space object (or deep sky ) is a term often used in amateur astronomy to refer to celestial objects that are not from the Solar System (such as planets, comets, and asteroids), nor individual stars or multiple star systems. Normally, these objects are not visible to the naked eye, but the brighter ones can be seen with a small telescope or even powerful binoculars.

A deep space object: Galaxy NGC 4526 and supernova SN1994D (Virgo constellation).

Types of deep space objects:

• Star clusters
  • Open clusters
  • Globulary clusters

• Nebulae
  • Bright nebulae
    • Emission nebulae
    • Nebulae of reflection
  • Dark nebulae
  • Planetary nebulae
• Galaxy
• Quasares

They are classified according to the Messier Catalog in 110 objects and the New General Catalog (NGC), much more complete, contains about 8000 objects. Many of these objects and others included in more specialized catalogues, such as the Uppsala General Catalog (UGC), allow amateur astronomers to demonstrate their observing skills and test their equipment. So-called Messier marathons are held on certain days of the year and observers try to spot all 110 objects in a single night. A much more demanding test based on the list is designed to test larger telescopes.