Charles Messier discovered M23 = NGC 6494 = h1990 on 20 June 1764. On 18 Jun 1784 (sweep 230), WH recorded "a cluster of beautifully scattered large stars, nearly of equal magnitudes; (visible in my finder) it extends much farther from the field of the telescope will take in, and in the finder seems to be a nebula of a lengthened form extending to about half a degree." JH made 3 observations, logging on sweep 269 ( 15 July 1830) "A star 10m in the centre of a beautiful discrete cluster of 60 or 70 stars 10 and 11m and one of 9-10. They run in lines and arches. It is loose and straggling, and the sky around it has a dotted appearance."

200/250mm - 8" (6/29/84): bright, fairly large with long star lanes to the edge of the field.

300/350mm - 13.1" (6/29/84): bright, large, rich, appears fully resolved. Very pretty open cluster.

400/500mm - 18" (8/12/10): stunning bright, rich cluster at 175x with several hundred stars visible in the 35' field with a large number of mag 9-11 stars sprinkled throughout the cluster. Many of the stars are arranged in long chains and loops with a distinctive chain of 5 stars curving NNW to SSE near the center and a longer curve of stars to the southwest. A string of stars heads NW out of the cluster to mag 6.5 HD 163245 outside the field. The stars are fairly evenly distributed with the density gradually thinning towards the edges. Two catalogued double stars are ARA 718 (10.9/12.3 at 5") near the center and ARA 719 (9.8/13.0 at 15") on the SE side. The Milky Way has a bright background glow just west of the cluster.

Notes by Steve Gottlieb