The INT is controlled by a Perkin-Elmer 3220 computer interfaced through CAMAC. The software drives the main HA and Dec axes, the Cassegrain Instrument Rotator, the Focus and the Dome and Shutters, and the computer provides an interface to the Autoguider.
The Telescope Operator interacts with the telescope via commands typed at the User Interface terminal, to be found in the control room, or by pushing buttons on the Control Desk or the handset, e.g. to make the telescope slew or adjust the tracking rate. These buttons are of a special design which ensures that, even when held down, the actions are only performed once, except for the guider buttons, which act continuously. Most of the buttons acknowledge that they have been pressed by lighting up.
Data can be entered into the control system via the User Interface. In particular, it is possible to set up a catalogue with position of up to 500 objects, which is held in memory. The coordinates may be entered with simple commands or loaded from disc files: catalogues of photometric, spectrophotometric, and astrometric standards are available. Further, one may enter telescope parameters such as offsets or tracking rates.