A telescope designed specifically for observations in the infrared part of the spectrum. Infrared telescopes are similar to optical Cassegrain reflectors, but designed to minimize the amount of infrared radiation reaching the detector from the telescope itself. Since infrared wavelengths are longer than those of visible light, the optical quality of an infrared telescope is less critical. The main mirror can be made thinner and the supporting structure lighter than in an optical telescope. However, modern large optical telescopes are designed for good performance in both the visible and infrared parts of the spectrum. The two most important ground-based infrared telescopes are the NASA Infrared Telescope Facility (IRTF) and the United Kingdom Infrared Telescope (UKIRT), both at Mauna Kea Observatory, Hawaii.