TNG - Telescopio Nazionale GALILEO

General Description

	Technical Specifications
	Images of development phases
	Development information in the TNG Newsletters

The TNG is a 3.5-m telescope with an alt-azimuth mount and Ritchey-Chretien configuration with two Nasmyth foci and active optics control. See technical specifications .

The idea to provide Italy with an optical national facility has been in the astronomers' mind since the early sixties, but the real beginning of the Galileo Project was in 1988, when the Council for Astronomical Researches (CRA) entrusted the Observatory of Padova with the feasibility study of a 4-m class telescope, and then in 1989 took the resolution to build the instrument following the design and optical innovations of the New Technology Telescope of the European Southern Observatory.
Some modifications have been necessarily introduced to fully exploit the latest technological developments in the fields of optics and informatic control, and to improve flexibility of use. These concern mainly movement control of the secondary and tertiary mirrors, the possibility to implement in the future more focal stations, the location of the control room outside the rotating dome itself and the total height of the instrument above ground, increased by around 5m due to site configuration.

Movement of the TNG is supplied by eight brushless motors (four for each axis), while telescope position is determined by two encoders with an angular resolution of +/- 0.06 arcsec.

The TNG building is a structure 24m in height, composed by a rotating octagonal dome, a lower rounded building enclosing the central pillar and an annex one-story service building.

The central pillar is a reinforced concrete hollow cylinder 960cm high. In the lower building, between the pillar and the external wall, there is ample storing space, while the annex structure houses auxiliary generators, technical offices and shops, laboratories, and - most important - the control room. Towards the South a bridge connects the observing floor to the existing upper road.
As is well known, thermal stability is an uppermost requirement to optimize imaging capabilities. To this end an effective air conditioning system has been carefully developed. A further control of air flow in the telescope area is given by five tiltable flaps set in the rear wall of the dome, and by a movable screen in the front wall.

The site selected for the TNG is in the Canary Island of La Palma, near the top of the Roque de los Muchachos, at an altitude of 2358m, about five hundred meters west of the Nordic Optical Telescope.

This is one of the best sites for optical astronomy, at a latitude of +29 degrees, protected most of the year by an anticyclon which prevents access to storms. The typical wind flow does not create problems to observations because it carries homogeneous oceanic air. The best period is around May, with almost 90% of photometric nights.

The Galileo Telescope is part of the Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias and is scheduled for first light in 1997.

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