The 1.06 m (42 in) MLO 40-inch Telescope is a Cassegrain reflector built by Astro Mechanics in 1966. It was originally fitted with a 1.02 m (40 in) primary mirror which has since been replaced. It is known informally as the Illinois telescope because it was located at UIUC's Prairie Observatory until 1981.[4] The 0.6 m (24 in) Clifford Smith 24-inch Telescope is a Cassegrain reflector.