The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), is a gamma ray detector located near Albuquerque, New Mexico. Observations with STACEE began in October 2001 and concluded in June 2007. Gamma rays were observed from objects such as the Crab Nebula, a supernova remnant, and Markarian 421, a blazar. STACEE uses the heliostats and space on the receiver tower of the National Solar Thermal Test Facility (NSTTF) operated by the Sandia National Laboratories on the grounds of the Kirtland Air Force Base. In the daytime, the facility is used for solar energy research. During the night STACEE uses the heliostats to reflect the brief flashes of Čerenkov radiation caused by gamma rays hitting the upper atmosphere to photodetectors mounted in the tower.