#OTD in 1801.
French astronomer Jean-Louis Pons makes his first comet discovery, jointly attributed to Charles Messier. In the next 27 years he discovers another 36 comets, more than any other person in history.
He appears to have used telescopes and lenses of his own design; his "Grand Chercheur" ("Great Seeker") seems to have been an instrument with large aperture and short focal length, similar to a "comet seeker".