John Herschel discovered NGC 6398 = h3694, along with NGC 6403, on 7 Jul 1836 and recorded "eF; S; R; almost certain it is not small double star. Definition much improved. It is certainly a nebula, and with long attention, I see another NGC 6403], still fainter, exactly on parallel, and 30 seconds following." His position is accurate.

Nevertheless, the RNGC classified both galaxies as nonexistent (Type 7) probably because DeLisle Stewart reported "eF, hazy * only" based on plates taken at Harvard's Boyden Station, in Arequipa, Peru.

600/800mm - 25" (4/5/16 - Coonabarabran, 318x): moderately bright and large, slightly elongated N-S, 45"x35", strongly concentrated with a bright core surrounded by a faint halo. A mag 14.5 star is at the west edge and a mag 15.5 star is at the northeast edge. A mag 12.5 star (close double) is 1.3' NW. Situated in a rich Pavo star field. Forms a pair with NGC 6403 4.7' ENE.

Notes by Steve Gottlieb