William Herschel discovered NGC 6304 = H I-147 = h3670 on 30 Apr 1786 (sweep 559) and recorded "vB, R, gmbM, between 2 & 3' dia. A very pretty object. A miniature of M62." His position is accurate. JH made two observations from the Cape of Good Hope and described the cluster on sweep 478 as "B; R; at first s, the vgvlbM; brighter part 2' diam; but there is a much fainter portion which extends a good deal further; stars 16-17 mag."

400/500mm - 17.5" (8/27/92): fairly bright, moderately large, slightly elongated E-W. The brightest portion is 2' diameter although a very faint halo increases the diameter to 3'-3.5'. Appears flattened on the south or southeast side. There was no significant central condensation although the central region was very mottled and a few faint mag 15-15.5 stars popped in and out of view. Within the faint halo 10-20 very faint mag 15-16 stars are just resolved.

Notes by Steve Gottlieb