Albert Marth discovered NGC 3643 = m 221, along with NGC 3644, on 22 Mar 1865 and noted "eF, vS". His position matches CGCG 039-136 = PGC 34802.

The RNGC misidentifies CGCG 039-143 = PGC 34817 as NGC 3643 (listed in my RNGC Corrections #2). See Harold Corwin's NGC notes for more errors in the modern identifications.

400/500mm - 17.5" (4/4/92): very faint, fairly small, elongated 2:1 NW-SE. A mag 13 star is at the SE edge 1.0' from center. NGC 3644 lies 12' S.

600/800mm - 24" (5/20/20 and 5/24/20): fairly faint, elongated 2:1 ~E-W, brighter core, 40"x20", overall fairly low surface brightness. A mag 13.2 star is 1' SE of center.

SN 2020hvf, a Type Ia supernova in NGC 3643, was discovered about a month ago (Apr 21) at 22" E of center (at the east edge of the galaxy). At 13th magnitude, the SN was similar in brightness to the mag 13.2 star just 45" to its SSE, and was bright enough to detract from viewing the galaxy!

Notes by Steve Gottlieb