Lacaille’s Octans
Lacaille’s Octans was positioned with no real regard to the stars that compose it, except for Eta (η) Octantis on the octant’s pivot, and that star is only magnitude 6.2. The southern pole star, Sigma (σ) Octantis, magnitude 5.4, was not labelled on Lacaille’s chart, although it was listed in his catalogue; it is actually the rightmost of the triangle of stars below centre of the picture, closest to the little telescope. Clearly, Lacaille did not regard his new constellations as recognizable star patterns but simply areas of sky in which he could commemorate the main instruments of the arts and sciences of his era.
This illustration comes from a copy of Lacaille’s original map of the southern stars included in the Atlas Céleste of Jean-Baptiste Fortin. Here the constellation is given the French name l’Octans de Reflexion, but Lacaille shortened it to just Octans on the second edition of his chart, published in 1763.
(Image: Author’s collection)
