William Herschel discovered NGC 2266 = H VI-21 = h403 on 7 Dec 1785 (sweep 486) and recorded "a very rich and very compressed cluster of stars of about 4 1/2 or 5' diameter, 5 or 6 of the largest stars are in a row." His position is on the southeast side of the cluster. John Herschel noted his position from 24 Dec 1827 (sweep 115) was "the most condensed part of a p rich, p comp cl of stars 11...15m; irreg figure; diam of most compressed part = 3...4'' triangular."

300/350mm - 13.1" (12/22/84): three dozen stars mag 9-15 in a 4' diameter. Most members are very faint and the cluster appears quite rich with averted over unresolved background haze. The brightest star, mag 8.6 SAO 78670, is at the southwest edge of cluster and a string of five brighter stars mag 10-12 trail to the ENE. An isolated mag 10 star is off the northwest corner.

Notes by Steve Gottlieb