The first maps of the Moon

Before the telescope, the Moon had a face but no geography. Less than fifty years after the first telescopic drawing, it had maps, and most of the names we still use.

1609: Harriot draws first

On 26 July 1609, the English mathematician Thomas Harriot sketched the Moon as he saw it through a telescope: the first known drawing of a celestial body seen through one, more than four months before Galileo’s.¹ He later drew a map of the full Moon, but never published any of it, so his work long went unnoticed.¹²

1610: Galileo’s new world

Galileo turned his telescope to the Moon on 30 November 1609 and drew it at least five more times over the next eighteen days. Four of his drawings were engraved for the Sidereus Nuncius, the “Starry Messenger”, printed in Venice the following March: the first printed telescopic images of the Moon.³ Their message was radical. The Moon had mountains and valleys. It was a world, not a perfect heavenly sphere.³²

1645: Van Langren names it

The next step came from a practical problem: longitude at sea. During a lunar eclipse, observers far apart could time the moment the Earth’s shadow touched a given feature and compare their clocks. For that, they needed a map on which every feature could be named without doubt.² The first map of the full Moon drawn for that purpose, with all features equally clear, was made in 1645 by Michael Florent van Langren, royal cosmographer to the King of Spain.²⁴

His names were a map of patronage. The Infanta Isabella appears three times; Pope Innocent X and Louis XIV are there too, with many others.⁴

1647: Hevelius

Two years later Johannes Hevelius, a wealthy brewer of Gdańsk, published the Selenographia, the first book entirely devoted to the Moon. He ground his own lenses, built his own telescopes, observed for years and engraved the plates himself.² The book holds three large maps; the best-known proposed a complete set of names which, in the end, did not last.⁵

1651: Riccioli and Grimaldi

The names that won were printed in Bologna in 1651, in the Almagestum novum of the Jesuit Giovanni Battista Riccioli. His fellow Jesuit Francesco Grimaldi drew the map; Riccioli chose the names.⁶ Craters received the names of people, such as Plato, Ptolemaeus and Tycho. The dark plains were named after weather and moods: Mare Tranquillitatis, the Sea of Tranquillity, and Oceanus Procellarum, the Ocean of Storms.⁶⁷

Riccioli officially defended a fixed Earth, yet he gave bright craters near the Ocean of Storms to Copernicus, Kepler and Galileo, and named two craters close by for Grimaldi and for himself.⁶

1919–1935: one list for everyone

By the twentieth century the names varied from one atlas to the next. When the International Astronomical Union was founded in 1919, it set up a committee to put them in order. Its report, Named Lunar Formations by Mary Adela Blagg and Müller, appeared in 1935: the first systematic list of lunar names.⁸

The IAU still names the Moon. New craters honour scientists, engineers and explorers, who must have died at least three years earlier; seas and lakes keep Riccioli’s idea, with Latin words for weather and other abstract notions.⁹¹⁰

The pioneers have their craters too: Harriot, Galilaei, Langrenus, Hevelius, Riccioli and Grimaldi.¹¹