Heinrich d'Arrest discovered NGC 4090, along with NGC 4086, on 2 May 1864. He mentioned this galaxy in his description for NGC 4086 as 3' to the north but his position is 10 sec of RA too large and 1.3' too far south. He notes a mag 13 star 1.1' southeast, as mag 15-16 at 60" distance, so the identification is certain despite the poor position.

IC 2997, discovered by Bigourdan, is not identical to NGC 4090, as assumed in modern catalogues. See Corwin's identification notes.

400/500mm - 17.5" (3/28/87): faint, almost round, diffuse, fairly small. A mag 14 star is 1.1' SE of center. Located 3.7' N of NGC 4086 within the NGC 4065 cluster.

Notes by Steve Gottlieb