Philippe Loys de Chéseaux discovered NGC 6633 in 1745-46. Caroline Herschel rediscovered the cluster on 31 Jul 1783. She wrote, "About halfway from S Serpentarii [Ophiuci] towards Theta Serpentis, a cluster of large stars. I counted about 80. Messier has it not." On 30 Jul 1788 (sweep 850), William Herschel called it "a coarsely sc. cl. of L stars."

300/350mm - 13.1" (9/9/83): very bright, very large but loose and scattered. At 62x, 150 stars are visible in a 60' field with several bright stars on the SW side and many bright stars are outside this field including mag 5.5 SAO 123516 15' SSE. This is a naked-eye open cluster in dark skies.

Notes by Steve Gottlieb