Schmidt Telescope

In 1949, Stein proposed that the Specola purchase a second telescope of the modern Schmidt design. Pope Pius XII provided the funds from his personal fortune and a telescope was ordered from the firm of Hargreaves and Thomson of London. Five years later, work began on the construction of the Schmidt building, topped by its 8.5 meter diameter dome, joined to the Carte du Ciel building. The telescope was delivered in 1957, but several years were required for its installation and testing. It was only in 1962 that observational programs could begin.

The instrument has a spherical mirror 98 cm in diameter, with a 65 cm corrector plate (its aperture) mounted at the center of curvature of the primary near the tube opening. The focal length is 2.4 meters. The 20 x 20 cm photographic plate is placed at the focal plane, about half way down the tube. The usable field is about 5 x 5 square degrees, more than six times larger than that of the Carte du Ciel telescope. Like the Double Astrograph, it photographed the spectra of stars by placing objective prisms at the tube opening. The three prisms obtained for this telescope were among the most powerful in the world. 

This Schmidt telescope was used for about twenty years to study the evolution of star clusters by stellar spectroscopy and polarimetry. Unfortunately, light pollution from the surrounding towns made the site unusable by the early 1980s.