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Mapping the Moon in the Early 18th Century

Striking pair of maps depicting the surface of the moon, based upon the models of Johannes Hevelius and Giovanni Battista Riccioli.

The two spheres of the moon provide a comparative analysis of the topographical information and nomenclature of Riccioli and Hevelius. Between the two spheres is a model showing the phases of the moon, with the different lunar phases represented in the four corners of the image. The map is further embellished with cherubs using a telescope and Diana, the lady of the moon.

In 1647 Johannes Hevelius, a brewer from Gdansk, published his Selenographia, the first treatise devoted entirely to the moon. The work included for only the second time, a single map that showed all the features of the moon equally clearly--a composite view that pictured the Moon in a way it never appeared in reality but was accurate in its placement of individual features. Hevelius was truly a remarkable man of science, who made his own lenses, constructed his own telescopes, observed the Moon on every clear night for several years, drew his observations, engraved them himself and had the wealth to publish a sumptuous book at his own expense.

In Selenographia , Hevelius presented graphical depictions of every conceivable phase of the Moon, as well as three large plates of the full Moon: the first showing the ways the full Moon actually appeared through the telescope, the second showing the way a maker of terrestrial maps might represent it (using the conventions of geographers) and the third being a composite map of all lunar features illuminated (impossibly) from the same side. It is this last map that was to be used by astronomers during lunar eclipses. Hevelius also suggested a system of nomenclature based on earthly features.

Hevelius founded the science of selenography (after Selene, the goddess of the Moon) and showed astronomers how to represent heavenly bodies. All lunar maps since his time have used the convention of single illumination (although while he used morning illumination, modern maps use evening illumination after Van Langren's model). Hevelius also instituted the practice of showing the entire lunar surface visible from the Earth, which, because of librations, is greater than a hemisphere. Hevelius's nomenclature, although used in Protestant countries until the eighteenth century, was replaced by the system published in 1651 by the Jesuit astronomer Giovanni Battista Riccioli, who gave the large naked-eye spots the names of seas (Sea of Tranquillity, Sea of Storm, etc.) and the telescopic spots (now called craters) the names of philosophers and astronomers.

It should be pointed out that although Riccioli wrote his Almagestum Novum in which his map appeared to combat the Copernican theory, he was evenhanded in assigning names: Copernicus and Kepler were assigned prominent craters and even Galileo received his due. Giovanni Battista Riccioli first published his map of the moon in Almagestum nouum, published in Bologna in 1651. The Riccioli moon map is historically of great importance, as it provides the basis for the system of lunar nomenclature still in use. It is more properly referred to as the Riccioli/Grimaldi map, since the Jesuit optician Francesco Grimaldi was apparently responsible for the map itself, while fellow-Jesuit Riccioli invented the names (and wrote the book in which the map appeared). Thus the Sea of Tranquility (Mare Tranquillitatis) traversed by the Apollo astronauts acquired its name here, as Mare Tranquillitatis, as did such prominent lunar craters as Plato, Ptolemaeus, and Tycho.

Johann Baptist Homann Biography

Johann Baptist Homann (1663-1724) was a mapmaker who founded the famous Homann Heirs publishing company. He lived his entire life in Bavaria, particularly in Nuremberg. Initially, Johann trained to become a priest before converting to Protestantism and working as a notary.

In 1702, Johann founded a publishing house that specialized in engravings. The firm flourished, becoming the leading map publisher in Germany and an important entity in the European map market. In 1715, Johann was named Imperial Geographer to the Holy Roman Empire by Charles VI and made a member of the Prussian Academy of Sciences. Most importantly for his business, his reputation and contacts gained him imperial printing privileges which protected his publications and recommended him to customers. Johann is best known for this Grosser Atlas ueber die ganze Welt, or the Grand Atlas of the World, published in 1716.

After Johann died in 1724, the business passed to his son, Christoph (1703-1730). Upon Christoph’s early death, the company passed to subsequent heirs, with the name of the company changing to Homann Erben, or Homann Heirs. The firm continued in business until 1848.