Heinrich d'Arrest discovered NGC 5131 on 24 Apr 1865 with the 11-inch refractor at Copenhagen. His single measurement is very accurate and he noted a nearby mag 13 star, which he placed 9.7 sec of time preceding and 1 3/4' north.

400/500mm - 18" (6/21/03): unusual appearance as initially only noticed a very small, bright core ~15" diameter with a stellar nucleus. But extending ~E-W are very dim, thin extensions increasing the size to 45"x15". Forms a pair with IC 4239 6.3' ESE. Extremely faint IC 4238 3.3' S was not seen.

Notes by Steve Gottlieb