The telescope was designed by the French firm REOSC.
Its structure is very different from that of a classic telescope: there is no tube, and the optics are supported by an iron framework. Counterweights balance the telescope, in order to minimize the stress which could compromise pointing and tracking accuracy. The optical system is formed by a main mirror with a diameter of 152 cm, with a central hole, and by a secondary mirror with a diameter of about 60 cm. The secondary mirror is located in front of the main mirror at a distance of 4m, and reflects the light through the hole, into the observing instruments. REOSC also designed the dome, which was built by Comeva of Vicenza. The Ritchey - Chretien optical system has a wide (70-arcminute) corrected field. The building was designed by the Technical Office of the University of Bologna, in a joint project with the Astronomy Department, and relying on the experience developed by REOSC in the Haute Provence (France) and ESO (Chile) buildings. It has 3 floors. The ground floor has a 3.5 m ceiling and was designed to host the mirror-alluminizing equipment. On the first floor are the dark room, with a room for pre-exposure treatment of photographic plates, an office-living room and the control room of the telescope. The second floor hosts the telescope and has a large lifting platform as a general facility during maintenance and observations. The telescope is supported by two concrete pillars, which have independent foundations and no point of contact with the other parts of the building. This prevents that vibrations, produced by the movements of the dome and of the lifting floor, are transmitted to the telescope.
The instrumentation at the focal plane is supported by a box bolted to the main mirror cell. Always mounted on the box are an eye-piece giving a field vision of 10', and a television system used to check the field and to guide the telescope. Depending on the scientific programmes, different instruments can be mounted on the telescope, and it is possible to have several mounted at the same time. A 45 degree movable mirror reflects the light into the chosen instrument.
The main instruments presently operating at the Cassini telescope are:
a) a two channel photometer, used to study stellar variability;
b) BFOSC a multipurpose instrument for imaging and spectroscopy, with an EEV CCD (1340x1300 px). A Technical Report in Html format available in Italian and English .