The Isaac Newton Telescope (INT) has a 2.54-m diameter primary mirror. It uses a polar-disc/fork type of equatorial mount.

Traditional visitor-mode observations ceased in mid-June 2024. In 2025, the INT completed a major refurbishment to become a fully robotic telescope to support the operation of HARPS-3 (High Accuracy Radial velocity Planet Searcher), a next-generation "exoplanet hunter" designed to detect Earth-like planets orbiting Sun-like stars.

Once fully commissioned, 50% of the time on the telescope will be used to carry out the dedicated Terra Hunting Experiment (THE) observations. The remaining 50% of the time is Open Time, available to the community.