Astronomical Images : The full surface of the Moon

Johannes Hevelius

Astronomical Images

<p style='text-align: justify;'>The <i>Selenographia</i>, literally meaning 'descriptions of the Moon' was published by Johannes Hevelius (1611-1687) in 1647. In addition to descriptions of the surface of the Moon, the book also contained other telescopic observations by Hevelius, as well as explanations of instruments. The <i>Selenographia</i> is an unusual publication in the extent to which an author controlled the printed presentation of his work. The book contained observations made by Hevelius at his observatory using instruments (several of which he invented or improved upon), drawn and noted down by himself, then engraved by himself ' several images bear the signature: <i>auctor sculpsit</i> (the author engraved) ' and published at his own expense. This avoided complications and errors that might be introduced during the publication process by other artists and printers. The book itself contains a wide range of representations of the Moon, including a series of the surface of the Moon through its phases. 'Fig. O' is a composite of ninety observations made at Gdansk, with details of the different phases of the Moon assimilated into one Full Moon figure. Hevelius explains that the different shadings of the intaglio figure are meant to simulate the surface of the Moon. The bigger spots indicate lakes, double-horizontal lines the mountains and valleys, while peaks are expressed with circles. The lunar surface is shown as two interlocking circles in order to account for the changing visible area due to libration (oscillation of the Moon).</p>