I wonder why Messier did not catalog the galaxy in the lower left (NGC 3628)? It obviously is of enough visual magnitude to have been seen during his observation.
One: the comet he was following didn’t go close enough to the third.
Two: NGC 3628 has a lower surface brightness than the others. Of the six scopes that Messier used, none were of better light gathering power than a 2.4 in refractor. They had bigger mirrors, but, he was using speculum for a primary and it wasn’t known for great reflectivity.
He could have looked at the field and missed it completely.
Look up the NGC 3190 for a nice grouping in the head of the Lion.
Tough to say, considering it might have been mistaken for a comet, which is what he had studied early on.
http://www.seasky.org/space-exploration/astronomers-charles-messier.html
Great Comet of 1744
http://en.wikipedia.org/wiki/Great_Comet_of_1744
http://commons.wikimedia.org/wiki/File:Comet_with_six_tails.jpg
http://www.uh.edu/engines/comet1744.jpg
https://36.media.tumblr.com/7b70835f0d5decf406a2b1f2024c69a0/tumblr_nihyimynMO1qa9m0zo1_500.jpg
