Pierre Méchain discovered the northern component of M51 or NGC 5195 = H I-186 = h1623 on 20 Mar 1781 and commented "saw this nebula; effectively it is double. The center of each is brilliant and clear; distinct and the light of each touches each other." Messier mentioned this companion to M51 in his 1784 version of the catalogue in Connaissance de Temps, though it never received recognition as a separate Messier object. WH found it on 12 May 1787 (sweep 734) and recorded "B, S, R, vgbM. Just north of the former M51]." JH reported "B; R: vsbM to a star. This nebula is the companion of M51 and is figured with it."

LdR and assistants described NGC 5195 as probably a spiral on several observations and other details were noted. On 17 Mar 1855: "I have no doubt of a spiral arrangement of the smaller Nucl." On 16 Apr 1855: "The 2nd Nucl seems to be the proper prolongation of the spiral arm with which it is connected." On 18 Apr 1860: "I still think the small Nucl is shaped like an "S". On 12 Apr 1872: "The edge of the 2nd convol. is very nearly rectilinear on the south side."

300/350mm - 13.1" bright, fairly small, very irregular appearance. Forms a double system 4.6' N of M51 and connected on the east side by a faint spiral arm of M51 which trails north on the east side to NGC 5195. The following side is sharply cut-off due to dust and appears as a half disc.

900/1200mm - 48" (4/2/11): I was shocked by the detail and structure visible in the companion to M51 at 375x. The main 2' portion of the galaxy has a striking asymmetric appearance with an extremely high surface brightness "bar" perhaps 2'x0.8' elongated N-S with a sharp light cutoff on the east side. Attached on the east side of a bar is semi-circular "loop" extending about a 1' E and connected at the north and south end of the bar. The western loop portion of NGC 5195 was slightly brighter where it connected at the ends and the interior of this loop was irregularly darker. On first glance there appeared to be an obvious short "arm" connected to the northeast end of NGC 5195 heading south, but then I realized this was the long connecting arm from M51 that brightened in the last 1' where it attaches to NGC 5195. The entire connecting arm was always a prominent direct vision feature of the pair. The center of the bar was sharply concentrated with an extremely bright, quasi-stellar nucleus.

At least three distinct plumes of nebulosity (referred to as the "crown") extended from NGC 5195 to the north. A broad wing of hazy nebulosity begins near the NE end (at the end of the connecting arm) and sweeps 2' to the north in a gentle curve. A second shorter plume extends directly north from the north end of NGC 5195. Finally a mass of very low surface brightness nebulosity spreads to the west from the southwest end of the galaxy and clearly sweeps towards the north for ~2.5'.

Notes by Steve Gottlieb