Galileo telescope (122 cm)

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 cantiere b2
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 inaugurazione 47
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The idea of Giovanni Silva to provide the University of Padua with a telescope, comparable for importance to the major telescopes of the epoch (In Europe, the telescope of Berlin-Babelsberg Observatory), was realized when Carlo Anti became Chancellor of the University of Padua. In 1933 the project for the larger European telescope was approved by the dictatorship of such a period.
A special committee composed by Emilio Bianchi (Chairman of the Astronomical Commitee "Consiglio Nazionale delle Ricerche"), Giorgio Abetti (Acting Director of Arcetri Astronomical Observatory) and Giovanni Silva, considered different places for founding the mountain branch of the Padua Observatory. At the end, after a two years meteorological survey carried out by Giuseppe Crestani, the Asiago plateau was chosen for the altitude (1000 metres above sea level), the absence of light pollution, the high percentage of clear nights. The construction of the telescope started at "Officine Galileo", Florence.
The design of the buildings (dome and offices) was committed to Daniele Calabi. In the following years he fled in the United States as he suffered the persecution of the fascist regime. In the United States he became an esteemed and well-known architect, but he neither was invited at the Asiago Observatory's opening cerimony, nor was mentioned in the official talks.

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:

HIC ME POSUIT
UNIVERSITAS
STUDIORUM PATAVINA
AT ENIM OCULOS
SEMPER ADSUM GALILAEI
A.D. MCMXXXIX

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.

Photo gallery  - construction of dome -   photo by Daniele Calabi

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.

THE OPENING CERIMONY

"We are not wrong if we say that today we are dedicating to Galileo Galilei the best monument we could construct in the 3rd Century of his death".
This is the first sentence of the official talk of the Chacellor of the University of Padua, Carlo Anti during the opening cerimony for the Asiago Observatory, 1942 May 27. He had a very important role in the realization of the major European telescope, and for this reason he continued:
"I must confide that this Observatory is the work at which I gaze fondly and of which I am proud,   perhaps because it will serve a pure science".

Official talk of Giovanni Silva

Francesco Zagar, astronomer of Loiano Observatory, who was deeply involved in the realization of the telescope and, in particular, of the spectrograph, mentioned in his talk the successful meeting "of the two principal authors of this project ... the Chancellor of the University of Padua, Carlo Anti and our incomparable master Giovanni Silva who were able to realize an Institute that will leave an eduring scientific sign".

During the opening cerimony, Giovanni Silva was appointed Director of the Observatory of Asiago.

The tragedy of the second world war is only marginally mentioned in the official talks. Carlo Anti remembers that the telescope is "a work of peace inside the rumble of a terrible war" and Giovanni Silva refers to "the difficulties of  such a period, in which the Italian industries were engaged for the preparation of  war materials".

The official talk of Cussini

The economic situation in Italy, which was already difficult during the realization of the Observatory, became ruinous in the following years because of the war and the autarchy. After the second world war there was a slow renewal of activities, even the scientific ones. The astronomical research at the Asiago Observatory started in 1947, when it was possible to reconstitute the Research National Commitee (Consiglio Nazionale delle Ricerche, CNR). The Galileo telescope became indeed "a sign of progress and civilization", as it was in the wish of Francesco Zagar.

Official talks of the opening cerimony (in Italian):

Il cinegiornale Luce sull'inaugurazione del telescopio "Galileo"

 Historical photo gallery (dome, Galileo telescope, offices)

THE ASTRONOMICAL RESEARCHES

When the scientific work started at the Observatory, Giovanni Silva was the Director and Francesco Zagar, Ettore Leonida Martin, Antonino Gennaro and Salvatore Taffara were members of the staff. Zagar, Taffara and Gennaro moved in Asiagoin 1942, immediatly after the opening cerimony of the Observatory, to devote themselves to the astronomical observations with the new instrument, both in photometric and spectroscopic fields.
First of all, astronomers were engaged in a testing period, in order to determine the telescope's potentialities. They worked for the precise determination of latitude and logitude of the dome; for refacing the instrument, determining the flexures of the spectrograph and its resolving power. Those technical works were published in the first volume of Contributi di Asiago.
Apart from a few papers about the position of comets Oterma 1, Oterma 2 and Whipple-Fedtke, which were calculated from photographic plates obtained at the Newtonian focus of the Galileo telescope, the scientific activites of the Asiago Observatory started at the end of the war, when in 1946 the prismatic spectrograph was mounted at the Cassegrain focus. Moreover other instruments were acquired in order to analyse the photographic plates. With new devices it was possible to carry out different astrophysical works, in the field of the variable stars, nebulae and stellar clusters. The first volume of Contributi di Asiago contains: Posizione di tre nebulose planetarie (Zagar); Grandezze fotovisuali e fotografiche della Nova T CrB (Taffara); Sul moto proprio relativo di alcune variabili tipo SS Cygni (Mannino, Rosino); Osservazioni fotografiche e fotovisuali ed elementi provvisori della variabile ad eclisse LN Cygni (Taffara e Mannino); Periodo e curva di luce della stella variabile IV Cygni (Mannino); Velocità radiali di Zeta Ursae Majoris e nuovi elementi dell'orbita (De Strobel); Ricerche sugli ammassi globulari (Rosino); Grandezze fotovisuali della variabile BL Cassiopeiae (De Strobel) and others.

The Observatory of Asiago was the centre for scientific activities and observations for astronomers of all part of Italy and even of big international Institutes, such as Paris and  Manchester. This bright centre moulded a lot of astronomers and directors of other Italian astronomical Institutes: Zagar, resident astronomer in Asiago, became Director in Milan; Righini, became Director in Arcetri (Florence), Leonida Rosino, who became Director of Asiago first, in 1953, and of Padua-Asiago then.
From 1992 at the telescope's foci is mounted a CCD camera. The photographic plates made with the 122 cm telescope in the Archive of the Asiago Observatory are:

modalità number first plate last plate
imaging 9.718 6/5/1942 12/3/1997
spectroscopy (newtonian focus) 3.220 20/4/1958 9/10/1991
spectroscopy (cassegrain focus) 18.500 13/1/1947 25/1/1992

 

 

 

 

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