Astronomical Images : Lens-grinding lathe

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. The book takes the reader through all the stages of the astronomer's work, starting with constructing instruments, making observations, recording observations and then making inferences and summaries from those observations. One of the earliest images in the book is this figure of a lens-grinding lathe inside a room. Hevelius refers to the works of Descartes and of Marius Bettinus (author of <i>Apiaria universae philosophiae mathematicae</i> (1645)) with reference to the focal points of curved glasses, and says that those inexperienced in making curved lenses for telescopes should consult the work of Girolamo Sirtori (<i>Telescopium</i> (1618)).</p>