Lawrence Parsons, the 4th Lord Rosse, discovered NGC 3975 on 21 Feb 1874 and recorded as a "vF, vS knot" 17.2 sec preceding and 32" north of [NGC 3978]. "It was quite certainly and repeatedly seen by Lord Rosse and Copeland." This offset points to MCG +10-17-103 = PGC 37480.

This galaxy is mentioned in the UGC notes to[NGC 3978, though questioned if it is NGC 3975. See Harold Corwin's identification notes on Lewis Swift's IC 3166, which may be a duplicate observation.

400/500mm - 17.5" (4/13/91): extremely faint, small, round, very low even surface brightness, requires averted vision. Forms a pair with NGC 3978 2.0' ESE.

Notes by Steve Gottlieb