His knowledge of the night sky, coupled with acute vision and great patience, made him highly successful at comet-hunting. His first comet, in 1801 (now designated C/1801 N1), was the first of 37 (including co-discoveries)—still a record for visual discoveries. Most of these discoveries were non-periodic comets, but he did co-discover the periodic comets 12P/Pons–Brooks (1812) and 7P/Pons–Winnecke (1819). Two comets he found in 1805 were later identified as Comets Biela and Encke.