High Quality Content by WIKIPEDIA articles! The XO Telescope is a telescope located on the 3,054 m summit of Haleakala on Maui, Hawaii, formed by a pair of 200 mm telephoto lenses. It is used to detect extrasolar planets using the transit method. It is similar to the TrES survey telescope. The construction of the one-of-a-kind telescope cost $60,000 for the hardware, and much more than that for the associated software.