E.E. Barnard visually discovered IC 4603, along with IC 4604, around 1883, probably with his 5" refractor. In his 1895 paper "On a great photographic nebula near Antares", he stated "for fully ten or twelve years I have known of a vast region of nebulosity in Scorpius near Antares." In addition he referred to a note made 15 June 1892, "A couple of years ago [at Lick Observatory] I found 2 stars involved in a very large diffused nebulosity. They are strongly nebulous in the 6.5" and in the 12", but are best seen in the 6.5". The stars are about 8.5 and 9.5 mag, the following star being the brighter. They are 1.8° north and 42' preceding Antares [apparently IC 4603]. This region and preceding it for some distance seems to consist of a vast but very diffused nebulosity." At Lick he took an image of region on 23 Mar 1895 with the 6" Willard lens at Lick Observatory. He noted "the brighter and more complicated portions of the nebula center about Rho Ophiuchi, 22 Scorpii and a couple of small stars occupying the center of the equilateral triangle formed by Rho Oph, 22 and Sigma Scorpii." The "couple of small stars occupying the center" are involved with IC 4603.

400/500mm - 17.5" (6/30/00): this is a large, circular glow surrounding a 4' pair of mag 8/10 stars and part of the Rho Ophiuchi complex (2° north of Antares). The nebulosity extends roughly 8'-10' in diameter. The setting is quite eerie as the 50' field is nearly devoid of all stars - just two other faint stars. The field has a dull gray appearance as if it was weakly luminous.

Notes by Steve Gottlieb