R.J. Mitchell discovered NGC 7390 on 9 Sep 1856 while examining the NGC 7385 group. He noted, "the 2 last sf ones [NGC 7389 and 7390] are vvF". This galaxy was misidentified as GC 4848 [NGC 7389] in the offsets measured on 11 Oct 1873. d'Arrest missed NGC 7390 when he observed the cluster. The (estimated) NGC position is 3' too far north; a similar offset error occurred with[NGC 7389.

400/500mm - 17.5" (7/4/86): very faint, very small, round, low even surface brightness. Located 7.7' SE of NGC 7385 in a rich, compact galaxy group. Forms a close pair with brighter NGC 7389 3.3' NNW.

600/800mm - 24" (7/30/16): at 260x; faint to fairly faint, small, round, 15" diameter, fairly low even surface brightness. Situated 3.3' NNW of mag 9.3 SAO 108210 and 2.3' SSE of NGC 7789 in the NGC 7385 Group = WBL 688.

Notes by Steve Gottlieb