Noctua (Latin: owl) was a constellation near the tail of Hydra in the southern celestial hemisphere, but is no longer recognized.[1] It was introduced by Alexander Jamieson in his 1822 work, A Celestial Atlas, and appeared in a derived collection of illustrated cards, Urania's Mirror.[2] Now designated Asterism a, the owl was composed of the stars Sigma Librae, 4 Librae and 54–57 Hydrae, which range from 3rd to 6th magnitude.[3] [4]
The French astronomer Pierre Charles Le Monnier had introduced a bird on Hydra's tail as the constellation Solitaire, named for the extinct flightless bird, the Rodrigues solitaire, but the image was that of a rock thrush which had been classified in the genus Turdus, giving rise to the constellation name Turdus Solitarius, the solitary thrush. It has also been depicted as a mockingbird.[5] The boundaries of the constellation were defined as longitude 0° to 26°30' and from the ecliptic to 15° S.
The Noctua could be used as an observer's guide to try to detect de globular star cluster NGC 5694, of which the location is immediately west of it.