Astronomical Images : The principal figure 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. This extraordinary figure of the Moon is perhaps the most famous figure presented by Hevelius in the <i>Selenographia</i>. This 'Fig. T', 'the principal figure of phases and lunations', is essentially an abstracted version of 'Fig. R', 'the general table of the phases of the Moon', that showed the entire visible surface of the Moon. The figure is not completely spherical and lacks lines for the outer circumference, since that part of the Moon's surface which is visible depends on libration. Hevelius recommended this figure, also called 'iconismus' by him and shown in 'simple and finest lines', as the basis for others to record their observations, using the scales provided below the figures. He explains that these are available in 50s or 100s from himself or the bookseller, and warns the reader not to use any copied figures as they would not be sufficiently accurate.</p>