the construction

The first dome constructed in Asiago, to contain the Galileo telescope, was a magnificent marble structure. It is situated on a hilltop, 1050 above sea level. In the entrance of the dome was placed the dedication of the telescope to Galileo Galileo, in the 3rd centenary of the death:

The telescope and the rotating dome were constructed by Officine Galileo, Florence during the second world war. The cost for the whole project (instrument and dome), which was coordinated by the engineer Cussini, amounted to 1.400.000 Lira.

Photographic Album

The optical layout

The committee composed by Silva, Abetti and Bianchi, together with the Optic Institute conducted by Ronchi, supported the Officine Galileo, and in particular the engineer Giotti, for choosing the optical layout of the large telescope. At the end, astronomers and technicians decided for an instrument with which it would be possible to obtain different optical configurations. A parabolic primary mirror, with a diameter of 122 centimetres, is configured with a flat secondary mirror for the Newtonian focus, or with a hyperbolic secondary mirror for the Cassegrain focus. The focal lenght is 600 centimetres in the first case and 1913 centimetres in the second one (main optical parameters).

For the manufacturing of the primary mirror it was necessary to realize a tower, 16 metres hight. The optical control of the mirror surface it was applied Foucault method and Rochi grating. At the beginnig the mirror was silverised. For the periodic silvering and, then, for the allimination (from 1948), the mirror was first transported in other site. Then the observatory was equipped with the instrument for the allumination.

the mounting

The 122 centimetres telescope has an equatorial, English type, mounting. North and south piers support a polar axis with the tube offset and a counterweight (in which there is the motor for declination movements) which permits the equilibrium of the system around the polar axis.

The north support of the axis was realized in order to provide translation movement for the adjustment of the polar axis. The south support contains the motors of the whole system. North and south piers are connected by a structure which is independent of the foundation of the dome. It is based on the underground rock, to secure the best stability conditions to the telescope.

The mirror weight is 600 Kg. The mirror support was designed with great attention: it was necessary to avoid every tension to the mirror and, in the same time, to permit its movement for optical controls. For this purpose, the mirror support was made with 18 pans, connected three by three. With a complex system of balances, the mirror weight is homogeneously distributed on the pans. For the same reason, the mirror is encircle by a counterweight ring.

The fusion and the manufactoring of the metal structures of the telescope were a very difficult task: it was necessary to fuse the polar axis more than once to obtain the optimal result.

the dome

The rotating dome over the marble structure, realized by Officine Galileo, has an external diameter of 15 metres, and internal one of 14 metres. The aperture of the dome is allowed by two sliding ports. The weight of the rotating dome is about 50 tons and can be moved by 20 truck.

In order to reach the Newtonian focus, there is a platform with which it is possible to go up along the aperture of the dome.

the spectrograph

The first prismatic spectrograph mounted at the Cassegrain focus of the telescope was designed by the technicians of Officine Galileo in collaboration with the astronomers, in particular with Francesco Zagar. It was mounted at the telescope in 1946. With such a spectograph it was possible to obtain four different angolar dispersions.

At present, a grating spectrograph (Boller&Chivens) is operating at Cassegrain focus.

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