Heliograph

In 1893 the Specola obtained a heliograph, a telescope especially designed for photographing the Sun; it is shown here with the custodian, Carlo Diadori. It was the first of its kind in Italy.

It was constructed in Paris following the design of Prof. P. Jules Janssen of Meudon, the noted solar astronomer who discovered the gaseous nature of the solar chromosphere and the element Helium in the Sun. The telescope optics were produced by the Henry Brothers and the mechanical mounting was by Gautier. Its objective lens had a 14 cm aperture and a focal length of 2.15 m; additional optics produced an effective focal length of 4.4 meters and produced an image of the Sun 27.5 cm in diameter on the photographic plate.

The telescope was originally mounted on the terrace of the monumental Nuovo Braccio (New Wing) of the Pius VII Museum; for esthetic reasons it was covered by a sliding flat roof, rather than the traditional dome. Later it was moved to a small dome on the terrace of a building located where the Mater Ecclesiae convent of the Poor Clares was later built by Pope John Paul II (which became the residence of Pope Benedict XVI after his retirement).