William Herschel discovered NGC 3945 = H I-251 = h1006 on 19 Mar 1790 (sweep 953) and recorded "vB, perfectly R, BN with F chevelure joining to it by imperceptible degrees; the whole about 1 1/2' dia. CH's reduced position is 16 tsec of RA too small. JH made two observations and logged on sweep 344 "B; R; psbM; 60"; a star precedes 8 sec of time from neb in PA 215.9°."

400/500mm - 17.5" (4/13/91): bright, fairly small, slightly elongated, 2.0'x1.5'. The small, very bright core has sharp edges and appears mottled with bright spots. The slightly elongated halo is much fainter. Three stars are near; a mag 12 star is 1.3' SW and two mag 13.5 star lie 1.7' NW and 1.3' S.

Notes by Steve Gottlieb