Palermo: Reale Stamperia, 1792.
A fine copy, uncut in the original boards, of Piazzi’s account of the Palermo Observatory, which he established, and where he made the observations that led to his discovery, on January 1, 1801, of the minor planet Ceres.
Specola Astronomica includes Piazzi’s description of the astronomical instruments he had commissioned and assembled for the Palermo Observatory, the most famous of which was Jesse Ramsden’s vertical circle, illustrated on the plates in this volume. A “large theodolite-type instrument was the 5-foot vertical circle which Ramsden made for Piazzi’s new observatory at Palermo. Both Ramsden and Piazzi worked at this instrument, twice abandoned before its completion in August, 1789. The horizontal circle gave readings in azimuth read by a micrometer microscope, and the vertical, readings in altitude by two diametrically opposed microscopes. The divisions on the circles were illuminated by an inclined silver mirror fixed to each microscope, and the wires in the telescope eyepiece by transmitting light from a small instrument through the hollow tube-axis – two Ramsden innovations. This instrument, the finest complete circle hitherto made, formed the basis of Piazzi’s astronomical work. With it he catalogued nearly 8000 stars, compiled a valuable table of refractions, and attempted to measure the parallax of several bright stars. The great labour involved in the catalogue is the more remarkable when we consider that each star was observed several times before its position was decided” (King, History of the Telescope, pp. 166-8, with the circle illustrated).
Summoned in 1780 by the viceroy of Sicily to fill the chair of higher mathematics at the Academy of Palermo, Piazzi was encouraged to establish an astronomical observatory, “and toward the end of the 1780s Piazzi went to England in order to obtain the best possible equipment.
“In England, Piazzi met Maskelyne, William Herschel, and Ramsden… The most important result of Piazzi’s English visit… was the great five-foot vertical circle, a masterpiece of eighteenth-century technology, that he commissioned from Ramsden. It was installed in the observatory in the Santa Ninfa tower of the royal palace of Palermo in 1789, and is still preserved there. The Palermo observatory opened in 1790, and Piazzi was appointed its director, a post that he retained for most of the rest of his life.
“Having returned to Palermo, Piazzi took up the problem of the precise determination of the astronomical coordinates (direct ascension and declination) of the principal stars. Palermo was then the southernmost European observatory, and the favourable climatic conditions that it provided allowed him to study more stars than had been previously catalogued, with a greater degree of accuracy” (DSB).
Piazzi published two additional parts of this work, but without plates, in 1794 and 1806.
Lalande, p. 622 (“Ce grand et précieux ouvrage”).
Folio (370 x 255 mm), pp. xxxii, 240 and 4 folding engraved plates (the first plate showing Ramsden’s vertical circle measures 650 x 470 mm). Uncut and completely untouched in the original carta rustica, a very fine, fresh, and crisp copy. Rare.