Centaurus is a large, bright southern constellation, one of Ptolemy's forty-eight, representing a centaur, often identified with the wise Chiron, teacher of heroes. It contains two of the most notable stars in the sky: Alpha Centauri, the closest star system to the sun, whose faint companion Proxima Centauri is the nearest star of all, and the brilliant Beta Centauri; together they serve as pointers to the neighbouring Southern Cross. In myth the centaur is shown holding or spearing the neighbouring Lupus, the wolf or beast. In astronomical tradition the constellation is a star pattern rather than a zodiac sign, distinct from the separate figure of Sagittarius the archer-centaur on the ecliptic. These are the features of Centaurus as the classical and modern traditions describe it, distinct from any astrological use of the region.
Several of Lacaille's eighteenth-century instrument constellations, Norma the level, Circinus the compasses, and Telescopium itself, were carved from the stars around Centaurus and Ara in the 1750s, so that a region of sky the classical tradition rendered as a single continuous mythological scene, centaur, beast and altar, now also carries the names of a set square, a pair of compasses and a telescope tucked into the gaps between the older figures.