R.J. Mitchell discovered NGC 531 (along with NGC 542) with Lord Rosse's 72" on 16 Oct 1855 while observing NGC 529 and 536 (found earlier by the Herschels). His position is 28 sec of RA west of UGC 1012 = PGC 5340, but the sketch confirms the identity. The error in the position was caused by a confusion in the reference object. PGC 5340 is not identified as NGC 531 in UGC (1012), CGCG (521-024) or MCG (+06-04-020). Carlson advocated removal of NGC 531 from the NGC. See Thomson's Catalogue Corrections and WSQJ April 1986.

400/500mm - 17.5" (8/31/86): faint, fairly small, oval SW-NE, fairly small. A mag 12 star is just off the NE end 1.0' from center. Member of the NGC 529-536 group = HCG 10 with NGC 536 3.1' SSE.

Notes by Steve Gottlieb