Rome: Giovanni Maria Salvioni, 1728.
First edition of the first book of telescopic observations of the planet Venus, including descriptions and illustrations of the dark spots on the surface of Venus; the work also contains important illustrations of lunar topography. Bianchini’s book is perhaps best known today for two often reproduced plates of aerial telescopes, of extremely long focal length, with lenses by Campani..
First edition of the first book of telescopic observations of the planet Venus, including descriptions and illustrations of the dark spots on the surface of Venus; the work also contains important illustrations of lunar topography. The erudite Roman historian and polymath Bianchini (1662-1729), who worked in the papal court and was a specialist in calendar reform, 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. “In 1728 he published Hesperi et Phosphori nova phaenomena, the first book ever to be written about the planet Venus. Bianchini described in detail his discovery – or discovery claim – of patches and other markings observed on Venus and also his determination of the planet’s period of rotation, for which he got a value entirely different from the one obtained by [Gian Domenico] Cassini: whereas the latter had found 23-24 hours, Bianchini concluded that the planet turned around itself in 24 days and 8 hours. Equipped with one of the excellent telescopes of the Roman telescope maker Guiseppe Campani – whose telescopes were also used by Cassini – he thought to have identified several Venus ‘continents’ and ‘oceans’ which he proposed to name after Portuguese and Italian celebrities (his oceans included a mare Columbi, a mare Vespucci and a mare Galilei)” (Kragh, p. 22). Bianchini also concluded, on the basis of several successive observations, that the north pole of Venus’s rotation was elevated 20 degrees above the plane of the ecliptic, and that the axis kept parallel to itself during the planet's revolution around the sun. Although his results on the rotational period were incorrect, due to Venus’s thick cloud cover, his observations were pioneering efforts in investigating the planet. Bianchini’s text is also important in the history of lunar cartography, notably for 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. “This 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 valleys” (Ashworth). Bianchini’s book is perhaps best known today for two often reproduced plates of aerial telescopes, of extremely long focal length, with lenses by Campani. 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 of the King of Portugal. A putto presents a globe of Venus to the King's portrait; other astronomical instruments are also depicted. The figure of Atlas supports the celestial globe on which the constellations are visible.
Bianchini’s observations of Venus began in July 1716, when he attempted to measure the diurnal parallax of the planet; these observations are described in Chap. VII of the present work. “This will solve a most pressing problem in Cosmology, Astronomy and Physics, namely the size of the Solar System, which follows as a direct corollary from the observation of Venus’ parallax, and is fixed so finely and accurately by this method that we can hardly expect equal certainty, it seems, from any other observation undertaken hitherto” (Heilbron, p. 71). The method was invented by Cassini, and involves measuring the change in apparent position of Venus due to the change in the position of the observer as the earth rotates. To notice this change, it is necessary to have in the same field of view some ‘fixed’ star as a reference point. “On 3 July 1716 Venus and [the star] Regulus came close enough to make possible a parallax measurement by Cassini’s method. Bianchini was ready, in a darkened room in a palace on the Palatine Hill put at his disposal by Clement XI. The telescope of 23 palms (5.1 m) detected both bodies during daylight and, although awkward, did not present a problem to Bianchini” (ibid.). He deduced a diurnal parallax of 14.3 seconds, close to the modern value. Bianchini attempted to repeat his observations in 1724, using Sirius as the marker star, but this led to a less exact result.
“That did not exhaust the charms of Venus. Bianchini had access to a lens of 94 palms (21 m) with which he thought he might observe her surface features – if she had any. He began his prying with Venus as evening star and with maximum elongation; he consequently sought a site with a rise toward the West of some 25 feet. He would then have to build a platform only 20 feet high to support the objective lens with which to study Venus around sunset, when its elevation was 40 degrees. Only two sites in Rome would do, the better being the garden of the Barberini palace on the Quirinale, built by Galileo’s one-time friend Pope Urban VIII. From there Bianchini found blemishes on Venus’s face that even the great Cassini had missed – although, as a Jesuit learned in astronomy informed him, Cassini had glimpsed a spot in 1677 and 1678. Bianchini gracefully acknowledged the possibility of this priority and asked [Cassini’s assistant] Maraldi to search Cassini’s manuscripts for information that would enable him to identify the spot and name it after its discoverer. If he had been able to see further, Bianchini wrote, it was not by standing on the shoulders of other astronomers but by using longer lenses.
“The first successful observations from the Barberini gardens took place in February and March 1726 in the presence of several distinguished gentlemen including a Scottish nobleman called Hope [presumably the Earl of Hopetoun] and a Spanish duke. The magnification of 112 made markings along the terminator as large as lunar features appeared to the naked eye. Consequently, as Bianchini warned, only observers could be depended on who could make out the Moon’s maria without the aid of a telescope. (Here he had excellent credentials having spotted an obscure rift, or lunar alpine valley, between the craters Plato and Aristotle.) Corroborated by keen-eyed observers, Bianchini deduced from the motions of the markings and the relative positions of the sun, earth and Venus that Venus rotated once in 24 days on an axis that inclined 20 degrees to the ecliptic. The figure now accepted for the rotation, 243 days, was first measured in 1964. From these and subsequent observations of 1726, Bianchini deduced a map of Venus. Contemporaries were astonished. No one had the vision, technique, or tools to duplicate the survey. Bianchini received many visitors eager to see the spots on the Mirror of Divine Beauty, the brightest of all bodies, the brilliant star of the morning” (ibid., pp. 72-73).
The work is dedicated to the Portuguese King João V (1689-1750), whose portrait appears on the engraved frontispiece. João V’s royal mathematician and astronomer, the Neapolitan Jesuit Giovanni Battista Carbone, had arrived in Lisbon on September 1722. On his way to Lisbon, in July 1722, Carbone had met Bianchini in Rome, and a friendly and frequent correspondence developed between them that would last until Bianchini’s death in 1729. In their letters the astronomers shared their data and thoughts on technical aspects of celestial observations. Some of Bianchini’s results were forwarded to the Royal Society by Carbone and published in the Philosophical Transactions. Making use of diplomatic channels and his royal status, Carbone succeeded in communicating and publishing Bianchini’s observations of a comet in 1723 and of a lunar eclipse the following year. Carbone and Portuguese diplomats also played a crucial role in the diffusion of new instruments — such as a reflecting telescope offered by João V to Bianchini.
“As a result of the exchange of favors between Bianchini and the Portuguese monarch the former’s opus magnum, the book Hesperi et Phosphori, was dedicated to Dom João V, the generous patron of the costly volume. In this work Bianchini presented detailed observations of the planet Venus and for the first time lavishly illustrated cartography of spots on the apparent surface of the planet. The author labelled these features in honor of several Portuguese historical figures. The dedication, inscribing the glory and power of the Portuguese king in the heavens, was framed and preceded by the cases of Galileo with his four Medician Stars and by Giovanni Domenico Cassini’s discovery of four moons of Saturn, dedicated to Louis XIV.
“As can be seen in the frontispiece of Hesperi et Phosphori a globe and a model of Venus‘ orbit are offered to the king of Portugal, apparently a strictly allegorical and symbolic representation. However, the depicted artifacts correspond in fact to real instruments sent to King João V that certainly were incorporated in his royal library at the Palace of Ribeira. On July 1728 Bianchini sent to Lisbon three wooden boxes and a tin tube containing a globe of Venus, the planet’s orbital model and several engravings and manuscripts. The gift was recorded in Bianchini’s correspondence. One of the boxes included the ‘golden metal machine’, an armillary model of the orbit of Venus, with which he intended to reward his Portuguese patron. The Venus Globe was in another box – excluding the earth and moon it is the first known planetary globe, and a wooden copy can still be admired in the Museo della Specola in Bologna.
“An engraving of the ‘golden metal machine’, clearly heliocentric, topped by King João V’s coat of arms can also be found in Hesperi et Phosphori. Bianchini explains in his book that the option for a heliocentric model did not imply that the true system was heliocentric – the armillary could be made to represent the Tychonic system; but that would increase its size at the same scale by 75 percent. So Bianchini, ‘for the sake of economy,’ preferred the smaller and the simpler model of the Venus orbit. As John Heilbron remarked, Bianchini became used to thinking in Copernican terms in spite of his ambiguous position, not favoring Copernicus or Tycho …
“As one of Bianchini’s astronomical correspondents, Giovanni Battista Carbone was part of an epistolary network that also included, among others, John Flamsteed, Eustachio Manfredi and the astronomers of the Paris Observatory. It was through this network that Bianchini tried to convince contemporary astronomers of the veracity of his observations of stable spots in the apparent surface of the planet, prior to the publication of Hesperi et Phosphori. In the summer of 1727 he sent to Lisbon a long-focus telescope by Campani hoping Carbone would confirm the Venusian spots. Apparently, Carbone never succeeded in the observation of the elusive spots, but the episode shows how Bianchini trusted in the observational capabilities of his Jesuit collaborator in Lisbon and how important was for him the Portuguese royal patronage” (Tirapicos, pp. 506-507).
In addition to his observations of Venus, “Bianchini discovered three comets: One was discovered on 30 June 1684, of which he was not only the discoverer but also the sole observer (C/1684 N1); another was a codiscovery on 20 April 1702 (C/1702 H1); and a third was on 17 October 1723, but which had already been seen, notably by William Saunderson, at Bombay (C/1723 T1). That of 1684 was last seen on 19 July, and its orbit was one of those determined by Edmond Halley. Bianchini’s attempt to measure the parallax of Mars at its opposition in 1685 gave a result not quite two-thirds of the true value. He observed many eclipses of the Moon, and saw the solar eclipse of 22 May 1724. He studied Jovian satellite phenomena, and made numerous drawings of the mountains and craters of the Moon, being credited with the discovery of the great Alpine Valley … Some idea of his skill, assiduity, and sagacity can be obtained from a selection of these observations edited, with a preface, by Eustachio Manfredi of Bologna (with a portrait of Bianchini as a frontispiece), published posthumously at Verona in 1737 [Francisci Blanchini ... Astronomicae, ac geographicae observationes selectae Romae, atque alibi per Italiam habitae ... una cum geographica meridiani Romani tabula a mari supero ad inferum; ex iisdem observationibus collecta et concinnata, cura et studio Eustachii Manfredi]” (Biographical Encyclopedia of Astronomers).
Honeyman 323; Graesse I, 437; Riccardi I, 132.15. Ashworth, The face of the moon, Linda Hall 11. Brown, Astronomical Atlases, Maps andCharts, p. 139. Heilbron, ‘Bianchini as an Astronomer,’ pp. 77-82 in: Kockel & Solch (eds.), Francesco Bianchini (1662-1729) und die europäische gelehrte Welt um 1700, 2005. Kragh, The Moon that wasn’t: The Saga of Venus’ Spurious Satellite, 2008. Tirapicos, ‘The old and the new Rome: Francesco Bianchini’s astronomical exchanges with the court of Lisbon,’ Mediterranean Archaeology and Archaeometry 16 (2016), pp. 503-508.
Folio (414 x 265 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). Contemporary vellum, spine lettered in manuscript (spine restored – not rebacked). A large fresh copy.