The Isaac Newton Telescope (INT) is a conventional Cassegrain-type telescope,
mounted on a polar-disk mounting. The telescope building is located
on the Canary Island of La Palma at an altitude of 2336 meters above sea level
(ground floor)
near the highest peak of the Caldera de Taburiente, an extinct volcano.
Its geographical
position is at longitude 17 5239.5(W) and
latitude 28 4543.2(N).
The telescope stands on its own pillar, separate from the rest of the
building, with its base about level with the second floor
(see Figure 
); the axes intersect at 14 meters above ground level.
The observing floor and control room are found on third floor.
A general desciption
of the INT and the observing site can be found in Vistas in Astronomy,
28, 1985.
The INT has a 2.54-m diameter primary mirror with a focal ratio of f/2.94. There are three focal stations, of which the f/3.29 Prime focus (with focal corrector) and the f/15 Cassegrain focus have been fully commissioned. The third, f/50 Coude focus was never implemented. Both Prime and Cassegrain foci are equipped with instrument rotators and autoguiders. In addition, the Cassegrain acquisition and guidance (A&G) box contains an integrating TV camera for field viewing. A second camera is attached to the wide-field finder telescope. This is used for locating guide stars for the autoguider and, to a limited extent, for field verification.
The telescope, the dome and shutters are normally operated by means of the
dedicated telescope computer, which resides in a
temperature-controlled clean room on the INT
building's second floor, to the west of the void, the so-called CLIP centre.
There one also finds power amplifiers for the telescope drive and much of
the telescope, TV and Autoguider electronics. The Control Desk and System
Console are located in the control room on the third floor,
together with the Engineering Rack,
which can be used, if necessary, for manual operation of the telescope system.
(First-time readers may read section at the end of this
chapter before continuing.)
A separate Instrument Computer is located in a small room on the third floor, adjacent to the control room.