The Isaac Newton Telescope (INT) has a 2.54-m diameter primary mirror with a focal ratio of f/2.94. It uses a polar-disc/fork type of equatorial mount, as illustrated in Figure . The corrected f/3.29 prime and f/15 Cassegrain foci have been commissioned. Both foci are equipped with instrument rotators and with 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 as an alternative to the Guide-Star Server (GSS) and, to a limited extent, for field verification. The INT is normally operated by a night assistant. Fuller details are given in the INT User Manual ( ING La Palma Manual No XX).
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Figure: Schematic views of the INT from the east and north.