Guillaume Bigourdan discovered NGC 5509 = Big 71 on 10 Jun 1887 (his last NGC discovery). There is nothing at the position in his second Comptes Rendus list, but he noted an error of 19' in polar distance in the remarks section of his 5th Comptes Rendus list (20 Apr 1891). Harold Corwin's re-reduced position matches CGCG 133-010 (his original error was 16'). CGCG 133-010 is not labeled NGC 5509 in the CGCG or MCG. RNGC and PGC misidentify PGC 50725, situated 3.5' NW of NGC 5508, as NGC 5509. See Corwin's identification notes.

400/500mm - 17.5" (7/17/01): faint, fairly small, round, 0.7' diameter. Weak, even concentration and no well-defined core. Occasionally, a faint stellar nucleus was glimpsed. Located 7' WSW of NGC 5513/MCG +04-34-004 and first of trio. This identification differs from the RNGC and PGC and this galaxy is not identified as NGC 5509 in CGCG, MCG or PGC.

Notes by Steve Gottlieb