William Herschel discovered NGC 3810 = H I-21 = h943 on 15 Mar 1784 (sweep 174) and noted "pB, L, lE, r." His position was 50 seconds of RA too far east. John Herschel made 5 observations, the earliest on 10 Apr 1823 (sweep 2), while still developing his sweeping technique: "vF; R; vgbM; a *9m 15' dist in parallel."

Several interesting observations were made at Birr Castle. On 18 Mar 1851, Bindon Stoney recorded "BM, F neby all round of a mottled charachter, knot or appendage in the p part. On 10 Apr 1852, he queried "Spriral? glbM." Dreyer, though, observing in 1878, comments "Beyond doubt a glob cl, outlying F branches on a F background which fades away gradually."

400/500mm - 17.5" (5/2/92): bright, fairly large, elongated 3:2 SSW-NNE, broad concentration, increases to brighter core but no nucleus, large very faint halo of dimensions 3.0'x2.0'. A group of three mag 11-12 stars mag is located between 9'-11' S.

Notes by Steve Gottlieb