John Herschel discovered NGC 3231 = h704 on 3 Apr 1832 (sweep 412) and recorded "A cluster of 20 stars more or less, 10,11, and 12m, scattered over a space of 10' dia. A star 7m south." Heinrich d'Arrest noted the principal star was double. This group is apparently an asterism although it stands out well on the DSS, being detached from the surrounding field.

400/500mm - 18" (3/5/05): 16 stars are visible in an 8' region. The stars are distributed into two groups oriented NW-SE. The northwest group stands out more distinctly as it is a bit richer and more compact (~2.5' diameter) and contains a mag 11.5/13 pair at 18". The sparser SE group also contains a mag 13 pair at 17". At the SE edge of the 225x field (9' SE of the NW grouping) is mag 7.9 HD 90318. Listed as an asterism in the RNGC.

Notes by Steve Gottlieb