CACTUS (Converted Atmospheric Cherenkov Telescope Using Solar-2) was a ground based Air Cherenkov Telescope (ACT) located outside Daggett, California, near Barstow. It was originally a solar power plant called Solar Two, but was converted to an observatory starting in 2001. The first astronomical observations started in the fall of 2004. However, the facility had its last observing runs in November 2005 as funds for observational operations from the National Science Foundation were no longer available. The facility was operated by the University of California, Davis but owned by Southern California Edison.