Giovan Battista Donati, Firenze, 1859 ca.

iron and wood, length 1600 mm

Florence, Museo Galileo, inv. 0582

This conical tube made of metal sheet, mounted on a wooden stand with three wheels and equipped with equatorial movement, was part of an apparatus designed by Donati between 1857 and 1859. The objective was a burning lens of 41 cm diameter and 158 cm focal length, made at the end of the 17th century, and now held in the Museo Galileo in Florence. In the focus of this lens was a single-prism spectroscope made according to the suggestions by Giovan Battista Amici, then director of the Specola. With this instrument, Donati examined and compared the spectra of 15 stars by measuring the angle of refraction of the main absorption lines. The results were presented in a Memoir completed in August 30, 1860 and published in Italian in 1862, in French and English in 1863, and later included in the Annals of the Museum of Florence in 1866 (see Fi. 02). A second plate from the same work shows the tube and the spectroscope used by Donati. With the same apparatus Donati was the first to observe the spectrum of a comet in 1864 (see Fi. 09).

Bibl.: DONATI 1866, CHINNICI 1999, MONACO 1994, BROGLIA & D’AVANZO 2007.

Foto: Museo Galileo, Firenze – Archivio Fotografico