Johannes Hevelius (1611-1687), Polish astronomer, at left, carrying out astronomical observations with his second wife Elisabetha Koopman Hevelius (1647-1693). They married in 1663. Hevelius, who worked in Danzig, was the founder of lunar topography: in 1647 he published his Selenographia, a chart of the Moon's surface that took four years to compile. As well as this, he observed sunspots and discovered four comets, and detailed the variability of the star Omicron Ceti, which he named Mira. Artwork from Hevelius's book Machina Coelestis (first volume, 1673).