BIANCHINI, Francesco Hesperi et Phosphori nova phaenomena sive observationes circa planetam Veneris unde colligitur. I. Descriptio illius macularum... II. Vertigo circa axem proprium... III. Parallelismus axis in oriba octimestri circa solem. IV. Et quantitas parallaxeos methodo Cassiniana explorata... Rome, Giovanni Maria Salvioni, 1728
Folio (388 x 272 mm), pp viii 92, with engraved frontispiece, title in red and black and with engraved vignette, two engraved initials, engraved headpiece, and two mezzotint engraved plates in text, and 10 folding engraved plates (the first in mezzotint); a fine, fresh, crisp copy in contemporary calf, spine panelled with gilt floral ornaments. £10,500
First edition, a fine copy of the first book of telescopic observations of the planet Venus, and containing important illustrations of lunar topography. The work also documents BianchiniÕs observations of the dark spots on the surface of Venus, and the Campani telescopes he used in his discoveries.
Bianchini (1662-1729) sought to determine the rotational period of the planet Venus from the dark patches on the disc, and to draw a map of its surface. Cassini had earlier determined a period of revolution or libration of about 23 hours; Bianchini concluded, on the basis of several successive observations, that the rotational period was in fact 24 and a half days; that the north pole of this rotation faced the 20th degree of Aquarius, and was elevated 15 degrees above the plane of the ecliptic, and that the axis kept parallel to itself during the planetÕs revolution around the sun. Although his results on the rotational period were incorrect, due to VenusÕs thick cloud cover, his observations were pioneering efforts in investigating the planet. He utilised an enormously long, single-lens long-focus refracting telescope, designed by the brilliant Roman lensmaker Giuseppe Campani.
Of great interest are the two mezzotint views of lunar features in the text. They depict the crater Plato and the Alpine Valley and were the result of the problems of determining topography from shadow patterns. ŌThis small engraving, which appears in the text as part of the introductory chapter, shows the crater Plato at the right, with Aristotle and Eudoxus at left, and the mountain range of the Alps cut by the dramatic slash of the Alpine Valley. Bianchini noted with surprise that the valley did not appear on the great Cassini map, and he was right; Bianchini was the first to see and to portray this most impressive of lunar valleysÕ (William Ashworth jr, The face of the moon p 11).
The fine frontispiece was engraved by Rocco Pozzi (d. 1780) after a design by Stefano Pozzi (1707-1768). It depicts Minerva on a throne, supporting a portrait the King of Portugal. A putto presents a globe of Venus to the KingÕs portrait; other astronomical instruments are also depicted. The figure of Atlas supports the celestial globe on which the constellations are visible. The Bologna Astronomical Museum has a globe of Venus made by Bianchini.
Riccardi I 132.15
£10500
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