Piscis Austrinus, the Southern Fish and Fomalhaut

Piscis Austrinus, the Southern Fish, here named Pisces Australis, is a southern constellation, one of Ptolemy's forty-eight, depicting a fish drinking the water poured out by the neighbouring Aquarius, the water-bearer. It is dominated by Fomalhaut, a bright first-magnitude star that stands rather alone in a dim region of the autumn sky and so is sometimes called the Lonely Star of Autumn; its Arabic name means the mouth of the fish. The constellation is regarded as the parent of the two zodiacal Fishes of Pisces, said to be its offspring. In astronomical tradition it is a pattern of stars rather than a zodiac sign. These are the features of Piscis Austrinus as the classical and modern traditions describe it, distinct from any astrological reading; Fomalhaut is one of the more notable stars of the southern autumn sky.

Piscis Austrinus lies near several of Lacaille's eighteenth-century southern constellations, Grus the crane and Microscopium among them, part of the same eighteenth-century programme that filled the deep southern sky, invisible from the Mediterranean world where the Ptolemaic forty-eight were first catalogued, with a mix of exotic birds and scientific instruments. Grus, the crane, and Microscopium, both introduced well after Ptolemy, fill much of the surrounding southern sky in a similarly instrument- and creature-themed eighteenth-century style.