John Herschel discovered NGC 2166 = h3012 on 2 Jan 1837 and recorded "F, S, R, gbM, 15"." His position is accurate. JH credits D 223 as the possible earlier discovery. James Dunlop found D 223 and/or D 222 on 27 Sep 1826. His description for D 222 reads "small round nebula preceding a small star." There is a "small star" just following the cluster, though his position is 9' too far west. D 223 has a relatively accurate position (1.6' N) with description "pretty bright and well-defined small round nebula." Both objects were recorded as observed once, though I don't know if they were on the same night.

600/800mm - 30" (10/13/15 - OzSky): at 394x; very bright, fairly small, round, 24" diameter, high surface brightness. Contains a relatively large bright core and smooth halo. A mag 12.5 star is off the northeast side [42" from center]. Located 6' S of mag 9.3 HD 41443. NGC 2177 lies 16' NE.

Notes by Steve Gottlieb