The 220 Mirrors of CRTF . ... Credit Copyright: NSTTF , Sandia National Labs , DOE Explanation: Even the largest of modern optical telescopes are small when compared with the light gathering power of the Central Receiver Test Facility (CRTF) located in New Mexico , USA. ... Recently, astronomers with the STACEE project have begun using CRTF to collect secondary light emitted when high-energy gamma rays strike the Earth's atmosphere. ... NASA Web Site Statements, Warnings, and Disclaimers . ...