Nicolas-Louis de Lacaille discovered NGC 6242 = Lac I-10 = D 520 = h3654 in 1751-1752 with a 1/2" telescope at 8x, during his expedition to the Cape of Good Hope. He simply noted an "elongated faint oval spot." James Dunlop observed the cluster on 13 May 1826 with his 9-inch f/12 reflector and recorded "a cluster or group of small stars, about 4' diameter, with branches extending S.p. and N.f., with considerable compression of the stars towards the centre of the group. This answers to the place of 155 Scorpii, but there is no nebula." He made 3 observations and his position is 4'-5' west of center of the cluster.

John Herschel first observed the cluster from the CGH on 5 June 1834 and logged "a p rich brilliant cluster of stars 10...12th mag, with one 7-8th mag near middle." Later in month (28 Jun) he recorded "cluster VI class, B, L, rich, discrete, 12', irregular figure, vlbM, fine object; place of a red star 9th mag, rest 11th mag, white." The next night he logged it as "a fine large rich cluster, class VII, stars 9..12th mag, fills field, place of a red star 8-9th mag in centre."

200/250mm - 8" (6/27/81): two dozen stars mag 8-11, fairly rich, compact, nice at low power. Faint stars are visible with averted vision.

400/500mm - 17.5" (7/16/93): ~100 stars in a 10' region at 220x, rich in faint stars. Includes red mag 7.3 SAO 101654 in the SE corner of cluster and 8 brighter mag 10-11 stars. Includes several curving arcs of stars with a few dozen mag 13 stars and a rich background carpet of mag 14.5-15.5 stars.

Notes by Steve Gottlieb