Deep-sky object

A deep-sky object (DSO) is any astronomical object that is not an individual star or Solar System object (such as Sun, Moon, planet, comet, etc.).^[1]^[2] The classification is used for the most part by amateur astronomers to denote visually observed faint naked eye and telescopic objects such as star clusters, nebulae and galaxies. This distinction is practical and technical, implying a variety of instruments and techniques appropriate to observation, and does not distinguish the nature of the object itself.

^ Fred Schaaf (1998). 40 Nights to Knowing the Sky: A Night-by-Night Sky-Watching Primer. Henry Holt and Company. p. 113. ISBN 978-0-8050-4668-7.
^ Ian Ridpath (2001). The Illustrated Encyclopedia of the Universe. Watson-Guptill Publications. p. 273. ISBN 978-0-8230-2512-1.

[1] Fred Schaaf (1998). 40 Nights to Knowing the Sky: A Night-by-Night Sky-Watching Primer. Henry Holt and Company. p. 113. ISBN 978-0-8050-4668-7.

[2] Ian Ridpath (2001). The Illustrated Encyclopedia of the Universe. Watson-Guptill Publications. p. 273. ISBN 978-0-8230-2512-1.

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