CHARA array

The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson, a 5,710-foot (1,740-meter) peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles. The observatory contains two historically important telescopes: the 100-inch (2.5 m) Hooker telescope, which was the largest aperture telescope in the world from its completion in 1917 to 1949, and the 60-inch telescope which was the largest operational telescope in the world when it was completed in 1908. It also contains the Snow solar telescope completed in 1905, the 60 foot (18 m) solar tower completed in 1908, the 150 foot (46 m) solar tower completed in 1912, and the CHARA array, built by Georgia State University, which became fully operational in 2004 and was the largest optical interferometer in the world at its completion. Due to the inversion layer that traps warm air and smog over Los Angeles, Mount Wilson has steadier air than any other location in North America, making it ideal for astronomy and in particular for interferometry. The increasing light pollution due to the growth of greater Los Angeles has limited the ability of the observatory to engage in deep space astronomy, but it remains a productive center, with the CHARA array continuing important stellar research. The initial efforts to mount a telescope to Mount Wilson occurred in the 1880s by one of the founders of University of Southern California, Edward Falles Spence, but he died without finishing the funding effort. The observatory was conceived and founded by George Ellery Hale, who had previously built the 1 meter telescope at the Yerkes Observatory, then the world's largest telescope. The Mount Wilson Solar Observatory was first funded by the Carnegie Institution of Washington in 1904, leasing the land from the owners of the Mount Wilson Hotel in 1904. Among the conditions of the lease was that it allow public access.

Mount Wilson is a peak in the San Gabriel Mountains, located within the San Gabriel Mountains National Monument and Angeles National Forest in Los Angeles County, California. With only minor topographical prominence the peak is not naturally noticeable from a distance, although it is easily identifiable due to the large number of antennas near its summit. It is a subsidiary peak of nearby San Gabriel Peak. It is the location of the Mount Wilson Observatory, which is an important astronomical facility in Southern California with historic 60-inch (1,524 mm) and 100-inch (2,540 mm) aperture telescopes, and 60-foot (18.3 m) and 150-foot (45.7 m) tall solar towers. The newer CHARA Array, run by Georgia State University, is also sited there and does important interferometric stellar research. The summit is at 5,710 feet (1,740 m). While not the tallest peak in its vicinity, it is high enough in elevation that snow can sometimes interrupt astronomical activities on the mountain. All of the mountains south of the summit are far shorter leading to unobstructed views across the Los Angeles Basin, Orange County, the Inland Empire, and out to Ventura County, San Diego County and the Pacific Ocean. On most days, Santa Catalina Island, some 65 mi (105 km) south, is visible. On clear days, other Channel Islands visible include San Clemente Island at 95 mi (153 km), Santa Barbara Island at 76 mi (122 km), San Nicolas Island at 107 mi (172 km), Santa Cruz Island at 98 mi (158 km) and San Miguel Island at 133 mi (214 km). At an elevation of 5,710 ft (1,740 m), the horizon on the ocean extends 92 mi (148 km). Mount Wilson is also heavily utilized for relay broadcasting of radio and television for the Greater Los Angeles Area.

KKLA-FM (99.5 MHz, "99.5 KKLA") is a commercial radio station licensed to Los Angeles, California and serving the Greater Los Angeles area. The station is owned by the Salem Media Group and broadcasts a Christian talk and teaching format. The KKLA-FM studios are located in Glendale and the transmitter is located atop Mount Wilson.

KSCA (101.9 MHz, "LA Nueva 101.9") is a commercial FM radio station licensed to Glendale, California and broadcasting to the Greater Los Angeles area. KSCA is owned by TelevisaUnivision, and it airs a Regional Mexican radio format. The station has studios and offices on Center Drive (near Interstate 405) in West Los Angeles. KSCA's transmitter is on Mount Wilson.KSCA broadcasts in the HD Radio format. Its HD2 subchannel airs a simulcast of KTNQ, a Spanish-language news/talk format. Its HD3 subchannel broadcasts Iranian programming known as "Radio Vanak". Its HD4 subchannel airs a simulcast of sister station KRCD, a Spanish classic hits format. KSCA is also broadcast on a 90-watt booster station in Santa Clarita, California, KSCA-FM1 at 101.9 FM.

KLCS (channel 58) is a tertiary PBS member television station in Los Angeles, California, United States. Owned by the Los Angeles Unified School District (LAUSD), it is one of eight television stations in the U.S. that are operated by a local school system. KLCS' studios are located at the former Downtown Magnets High School campus on West Temple Street in downtown Los Angeles, and its transmitter is located atop Mount Wilson. KLCS is one of four PBS member stations in the Los Angeles market; the others are KVCR-DT (channel 24) in San Bernardino, which serves the Inland Empire; KOCE-TV (channel 50) in Huntington Beach; and KOCE-TV's sister station KCET (channel 28) in Los Angeles, which KOCE-TV replaced in 2011 as the city's primary PBS station. Since the spectrum auction in 2018, when KLCS sold its physical channel, it has been a guest on KCET's channel 28 signal. KLCS remains the fifth most-watched public television station in the country.

KTBN-TV (channel 40) is a religious television station licensed to Santa Ana, California, United States, serving the Los Angeles area as the flagship station of the locally based Trinity Broadcasting Network (TBN). The station's offices are located at TBN's headquarters in nearby Tustin, and its transmitter is located atop Mount Wilson.

KSCI (channel 18) is a television station licensed to Long Beach, California, United States, serving the Los Angeles area. Owned by WRNN-TV Associates, the station airs programming from Shop LC. KSCI's studios are located on South Bundy Drive in West Los Angeles, and its transmitter is located atop Mount Harvard. KSCI served as a multicultural independent station until June 2021.

KTTV (channel 11) is a television station in Los Angeles, California, United States, serving as the West Coast flagship of the Fox network. It is owned and operated by the network's Fox Television Stations division alongside MyNetworkTV outlet KCOP-TV (channel 13). Both stations share studios at the Fox Television Center in West Los Angeles, while KTTV's transmitter is located atop Mount Wilson.

KCOP-TV (channel 13) is a television station in Los Angeles, California, United States, serving as the West Coast flagship of MyNetworkTV. It is owned and operated by Fox Television Stations alongside Fox outlet KTTV (channel 11). Both stations share studios at the Fox Television Center located in West Los Angeles, while KCOP-TV's transmitter is located atop Mount Wilson.

The Infrared Spatial Interferometer (ISI) is an astronomical interferometer array of three 1.65 m (5 ft 5 in) telescopes operating in the mid-infrared. The telescopes are fully mobile and their current site on Mount Wilson allows for placements as far as 70 m (230 ft) apart, giving the resolution of a telescope of that diameter. The signals are converted to radio frequencies through heterodyne circuits and then combined electronically using techniques copied from radio astronomy. ISI is run by the University of California, Berkeley Space Sciences Laboratory. The longest (70 m (230 ft)) baseline provides a resolution of 0.003 arcsecond at a wavelength of 11 micrometres. On 9 July 2003, ISI recorded the first closure phase aperture synthesis measurements in the mid infrared.

KNBC (channel 4) is a television station in Los Angeles, California, United States, serving as the West Coast flagship of the NBC network. It is owned and operated by the network's NBC Owned Television Stations division alongside Corona-licensed Telemundo outlet KVEA (channel 52). Both stations share studios at the Brokaw News Center in the northwest corner of the Universal Studios Hollywood lot off of Lankershim Boulevard in Universal City, while KNBC's transmitter is located on Mount Wilson.

KPCC (89.3 FM) – branded LAist 89.3 – is a non-commercial educational radio station licensed to Pasadena, California, primarily serving Greater Los Angeles and the San Fernando Valley. KPCC also reaches much of Santa Barbara, Ventura County, Palm Springs and the Coachella Valley, and extends throughout Southern California with five low-power broadcast relay stations and three full-power repeaters. Owned by Pasadena City College and operated by the American Public Media Group via Southern California Public Radio, KPCC broadcasts a mix of public radio and news, and is an owned-and-operated station for American Public Media; in addition to serving as an affiliate for NPR and Public Radio Exchange; and is the radio home for Sandra Tsing Loh and Larry Mantle. Besides a standard analog transmission, KPCC broadcasts over two HD Radio channels, and is available online. The studios are located in Pasadena, while the station transmitter is on Mount Wilson. It is one of two full NPR members in the Los Angeles area; Santa Monica-based KCRW is the other.