The word selenographia, a Latinized Greek noun derived from Selene (the moon), and graphia (from the verb graphein, to scratch, draw, write, represent, describe) was coined in the seventeenth-century to refer to textual and visual lunar description made from telescopic observations. From the 1640s, the word designates a map of the features of the satellite. In the production of these images, astronomers and artists engaged in graphical experimentation for the efficient translation of fragmentary views (it was impossible to see an image of the full moon at once through a seventeenth-century lens) into a detailed representation of the entire lunar disc. A gallery of seventeenth-century selenographies can be found here.
This image (Fig. 1) is perhaps the most abstract selenography of its time. The lunar features are not inscribed within a circle representing the limits of the disc but are floating on the blank page. The moon is not intended to look naturalistic: there is no expression of volume or tone as in the phases engraved by Claude Mellan under the direction of Pierre Gassendi and Nicholas Fabri de Peiresc or in the full moon drawn and engraved by Jean Patigny under Jean-Dominique Cassini. Here the depressions and elevations of the surface are reduced to irregular shapes engraved with a single line. A rhomboid grid marks an imaginary centre of the disc that was intended to orientate the user of the telescope. This is not a moonscape but a two-dimensional representation of the topography of the moon. Johannes Hevelius published the image in his lunar treatise, the Selenographia sive lunae descriptio, published in Gdansk in 1646.
Hevelius used this template to reconstruct more detailed maps of the full moon and the forty phases that illustrate the Selenographia. The template itself, called Figura Primaria Phasium et Lunationum (called Fig. T and its variant Tt) was inserted in chapter 44 of the book; and in many cases copies of the figures were bound at the end of the volume. Hevelius explained this picture as a synthesis of observations taken across a period of four years. He presented the image as an astronomical instrument that would serve the recording of lunar eclipses, the occultation of celestial bodies, and the calculation of terrestrial longitude. The astronomer could shade or mark lines over the image to show the progress of a lunar eclipse or the places of the conjunction of a planet. The author’s intention was for his map to be transferred on to copper plates so that it could be easily reproduced and used across the world. However, the template was perhaps not as helpful as Hevelius would have liked (Fig. 2).
Though engraving and etching was increasingly valued and practiced by amateurs throughout the seventeenth century, the reproduction of Hevelius’s template would have required not only knowledge of the craft and access to a roller press (or, these lacking, to an engraver) but also a real motivation. My survey of copies of this image in the archives of the Royal Society indicates that astronomers did not use Hevelius’s recording aid. Thus far, evidence suggests that they preferred to record lunar phenomena in tables and text rather than through illustration.
Hevelius’s correspondence and the copies of his papers do not frequently convey the results of observations through a visualisation: the earliest example of a communication accompanied by a lunar template representing the transit of Jupiter over the moon in September 1671 is found within the series now called Letter Book Original that gathers a selection of copies of autograph letters indexed by Richard Waller in 1689 (Fig. 3). This template is much smaller than the one printed in the Selenographia. The image was most likely sent with the intention of being published, for it was printed in the Philosophical Transactions to illustrate Hevelius’s communication.
In the volume holding Hevelius’s correspondence with Henry Oldenburg, only three observations, all pertaining to the later part of Hevelius’s life, are illustrated with this reduced version of the Figura Primaria: two lunar eclipses of 1676 and 1682, and an occultation of Jupiter of 1686. These are also appended to tables and texts. Arguably, Hevelius also sent these papers aiming for them to be published. It seems that he used these templates not as instruments but as visualisations to communicate observations effectively to an interested yet not specialised readership (Figs 4 & 5).
Remarkably, the lunar template is also scarce in observations sent to the Royal Society by other astronomers. Etched or pen and ink copies of Hevelius’s Figura Primaria are found in recordings of lunar eclipses taken between 1689 and 1690, which were sent by astronomers of the observatory of Nuremberg, Georg Christoph Eimmart and his collaborator Johann Philipp Wurzelbaur (Fig. 6). Notably, these astronomers also represented lunar observations with Hevelius’s template in self-published pamphlets promoting their work in Nuremberg in 1685 and in the periodical the Acta Eruditorum of 1686. Eimmart was an astronomer as well as an accomplished engraver but the fact that he was capable of making copies of Hevelius’s template does not explain why he and his friend decided to convey their results in this way (Fig. 7). I would like to understand if Eimmart and Wurzelbaur adopted Hevelius’s graphics in order to promote their work at the observatory of Nuremberg within his scientific legacy.
This example helps me continue my reflection about the purpose of lunar maps in the seventeenth century. The case of Hevelius’s Figura Primaria adds to a number of instances in which the motivation for producing maps of the moon is not purely astronomical. Thus far, I think that although the process of making selenographies is related to the desire to test technology and to further understand the topography of the satellite through observation and drawing, the publication of these images obeys the desire to promote a scientific identity.