The Zeiss Visual Refractor Telescope

In the early 1930s, plans for a new Specola at Castel Gandolfo were prepared by the firm Carl Zeiss of Jena. Construction began in 1932 and by 1935 it was mostly complete.

Inauguration: 29 september 1935 on the German mounting. The new visual refractor was installed under a large wooden dome 8.5 meters in diameter resting on the massive round construction of the palace’s ancient spiral staircase.

Zeiss provided a 40cm objective of 6m focal length, together with a set of 9 eyepieces and various accessories. The instrument was also provided with a Graff photometer for observing variable stars and with a micrometer for measuring double stars. Later on a Danjon stellar interferometer was added.

This was constructed in the Specola workshop and could be used for the determination of distances and positions of double stars and the diameters of planets.

Vatican Observatory 2025.09.27