John Herschel discovered NGC 6403 = h3695, along with NGC 6398, on 7 Jul 1836 and simply noted "eeF. The following of 2." His position, though 10 seconds too small, clearly applies to ESO 139-019 = PGC 60750. DeLisle Stewart recorded NGC 6403 "extremely faint, hazy star only", based on plates taken at Harvard's Arequipa station.

RNGC misclassifies the number as nonexistent. See notes for NGC 6398.

600/800mm - 25" (4/5/16 - Coonabarabran, 318x): moderately bright, fairly small, irregularly round, 30" diameter, broad concentration with a slightly bright nucleus. Situated in a rich Pavo star field with a mag 11.2 star 1.1' SSE. Forms a pair with NGC 6403 4.7' WSW.

Notes by Steve Gottlieb