13x80mm (1/20/07): visible in the finder as a very faint, small glow about a half-degree SW of M35.

William Herschel discovered NGC 2158 = H VI-17 = h375 on 16 Nov 1784 (sweep 317), immediately after discovering NGC 2129. He logged "a very compressed cluster of vS stars, very rich." On 24 Feb 1827 (sweep 59), John Herschel described the cluster as "rich; much compressed almost to nebulosity; stars very small; irregular triangular figure."

NGC 2158 was classified as a globular by Rosino in 1954 (Contr. Padova in Asagio No. 52), Helen Sawyer Hogg, 1959 (Star Clusters) and more recently in the RNGC due to its richness. Nevertheless, it is considered an intermediate age open cluster (~ 1 billion years old). NGC 2158 is also five or six times as distant as M35, as far as 16,000 light years away (5071 parsecs).

200/250mm - 8" (11/5/83): few stars resolved over haze.

300/350mm - 13.1" (2/16/85): at least 20-25 stars resolved at 415x.

13.1" (11/5/83): ~15-20 stars, mottled clump near SE edge.

400/500mm - 17.5" (2/8/86): 30-35 stars resolved, unusually rich, compact, about 5' diameter. The appearance is similar to a resolved globular cluster. Located 30' SW of M35.

Notes by Steve Gottlieb