Mount Laguna Observatory (MLO) is operated by the SDSU Department of Astronomy to support its research, training, and educational programs. Current institutional partners include the University of Illinois at Urbana-Champaign (UIUC) and the University of Kansas (KU). MLO is located 45 miles east of downtown San Diego at a dark site in the Cleveland National Forest at an altitude of 6100 feet (1859 meters).  This site is well protected from the urban lighting of the San Diego metropolitan area.  Its remoteness, along with the high percentage of clear nights and excellent seeing, makes Mount Laguna one of the best overall observatory sites in the continental United States.

The three major research instruments and their auxiliary equipment are: the 50-inch (1.25-meter) Phillips Claud reflector with KU, currently under construction (4K^2 CCD camera system); the 40-inch (1.0-meter) reflector with UIUC, manufactured by Astro Mechanics, Inc. (two CCD cameras, Cassegrain spectrograph, near-IR camera, automated photometer, Coude bench spectrograph); and the Clifford Smith 24-inch (0.6-meter) reflector (automated photometer, SBIG CCD camera).  Our students lead observational projects with these telescopes under the advisement of the faculty.  A five bedroom apartment building, four bedroom dormitory, and large shop building are also located on site. Instrument and CCD development are carried out at the on-campus mechanical and electronics shops. Observatory support staff includes a resident astronomer, an engineer, and the observatory superintendent.

Sky conditions at MLO are photometric 60% of the time and spectroscopic 75% of the time. The poorer weather usually occurs in late winter and early spring (February and March). The summer monsoon conditions that plague Kitt Peak in July and August are greatly moderated at MLO. The sky glow from San Diego and other urban areas contributes only about 5% at the zenith on moonless nights. Thus, on these dark nights, the sky brightness at the zenith in the Johnson B filter averages 22.8 magnitudes per square arcsecond. Seeing is generally less than two arcseconds and frequently less than one arcsecond.

The Reginald Buller 21-inch (0.5-meter) visitors’ telescope, manufactured by J.W. Fecker, Inc., is used for instructional support of our General Education Astronomy classes and labs and for special SDSU public outreach programs. This classic telescope has superb optics for viewing by eye.