1. A faint constellation in the southern hemisphere, containing the south celestial pole.
Usage: astronomy; proper noun when referring to the specific constellation
2. An ancient astronomical instrument used for measuring angles, especially the altitude of celestial bodies; a predecessor to the sextant.
Usage: historical; nautical

Examples

• Octans is one of the faintest constellations visible from Earth.
• The south celestial pole lies within the constellation Octans.
• Navigators once used the octans to determine their position at sea.
• Octans was named by the French astronomer Nicolas-Louis de Lacaille in the 18th century.
• The octans instrument could measure angles up to 90 degrees.