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Abbreviation Oct
Genitive Octantis
Pronunciation /ˈɒktænz/, genitive /ɒkˈtæntɨs/
Symbolism the Octant
Right ascension 22
Declination −90
Family La Caille
Quadrant SQ4
Area 291 sq. deg. (50th)
Main stars 3
Stars with planets 3
Stars brighter than 3.00m 0
Stars within 10.00 pc (32.62 ly) 1
Brightest star ν Oct (3.73m)
Nearest star LHS 531
(28.11 ly, 8.62 pc)
Messier objects none
Meteor showers none
Visible at latitudes between +0° and −90°.
Best visible at 21:00 (9 p.m.) during the month of October.

Octans /ˈɒktænz/ is a faint constellation of the southern sky. Its name is Latin for the eighth part of a circle, but it is named after the octant, a navigational instrument. The constellation was devised by Nicolas Louis de Lacaille in the eighteenth century.

The constellation Octans as it can be seen by the naked eye.

Octans is notable as the location of the south celestial pole. Unlike the north pole, it has no bright pole star: Sigma Octantis (σ Oct) is a naked-eye star very close to the pole, but it is so faint (mag. +5.45) that it is practically useless for navigation purposes. Conveniently for navigators, the constellation Crux, the Southern Cross, points toward the pole.

The constellation is circumpolar to the south celestial pole, so it can be seen in Southern Hemisphere skies during the evening in any month of the year. The Right Ascension and month of best visibility given are for the three brightest stars, which are at their highest in the sky during the evening in November.

Pole star(s)[edit]

Octans is the only constellation to hold two pole stars of two different planets of the Solar System; the south pole star of the Earth is Sigma Octantis and the south pole star of Saturn is Delta Octantis.

History and mythology[edit]

Octans was created by Nicolas Louis de Lacaille in 1759 out of faint circumpolar stars. Originally, it was known as "Octans Hadleianus" in honor of the octant's inventor, John Hadley, who devised it in 1730. There is no real mythology related to Octans, partially due to its extreme southerly latitude.[1]


Octans is a very faint constellation; its brightest star is Nu Octantis, a magnitude 3.8 star. Sigma Octantis, the southern pole star, is a magnitude 5.4 star about 1 degree away from the South Celestial Pole. Its faintness means that it cannot be used for navigation.[2]


USS Octans (AF-26) was once a United States Navy ship.


  1. ^ Staal 1988, p. 257.
  2. ^ Staal 1988, p. 258.
  • Ridpath, Ian; Tirion, Wil (2007), Stars and Planets Guide, Princeton University Press, ISBN 978-0-691-13556-4 
  • Staal, Julius D.W. (1988), The New Patterns in the Sky: Myths and Legends of the Stars, The McDonald and Woodward Publishing Company, ISBN 0-939923-04-1 

External links[edit]

Coordinates: Sky map 22h 00m 00s, −90° 00′ 00″