Hevelius , Johannes

(1611–1687) German astronomer

Hevelius was the son of a prosperous brewer from Danzig (now Gdańsk in Poland). He followed his father in the family business as well as devoting himself to civic duties. After studying in Leiden, he established his own observatory on the rooftops of several houses overlooking the Vistula, an observatory which soon gained him an international reputation.

He published several major works of observational astronomy. Four years' telescopic study of the Moon, using telescopes of long focal power, led to his Selenographia (1647; Pictures of the Moon). Making his own engravings of the Moon's surface he assigned names to the lunar mountains, craters, and plains taken from the Earth placing, with what the writer Sir Thomas Browne called witty congruity, “…the Mediterranean Sea, Mauritania, Sicily, and Asia Minor in the Moon.” This system of naming, apart from the Alps, did not survive long, Giovanni Riccioli's alternative system of scientific eponomy being preferred. Hevelius's star catalog Prodromus astronomiae (Guide to Astronomy) was published posthumously in 1690.

Hevelius is today best remembered for his ‘aerial’ telescopes of enormous focal length and his rejection of telescopic sights for stellar observation and positional measurement. He was widely criticized for the latter eccentricity and in 1679 was paid a famous visit by Edmond Halley who had been instructed by Robert Hooke and John Flamsteed to persuade him of the advantages of the new telescopic sights. Hevelius claimed he could do as well with his quadrant and alidade. Halley tested him thoroughly, finding to his surprise that Hevelius could measure both consistently and accurately. He is therefore the last astronomer to do major observational work without a telescope.