Samuel Oschin telescope

Samuel Oschin telescope. The Samuel Oschin telescope is a 48-inch (1.22-meter) Schmidt camera located at the Palomar Observatory on Palomar Mountain in California. Originally known as the Palomar Schmidt, it was renamed in 1986 to honor the philanthropist Samuel Oschin. For decades, this wide-field instrument has been a workhorse for major astronomical surveys, systematically mapping the northern sky and contributing to numerous landmark discoveries in astronomy and cosmology.

History and construction

The telescope was constructed in the late 1940s as a companion survey instrument to the famed 200-inch Hale telescope at the same site. Its design as a large-format Schmidt camera was spearheaded by Fritz Zwicky, who advocated for its construction to support his research on galaxy clusters and supernovae. The optics, including its 48-inch correcting plate and 72-inch mirror, were fabricated by the renowned American optical company Perkin-Elmer. The telescope saw first light in 1948 and was dedicated as the Samuel Oschin telescope in 1986 following a major gift from the Oschin family. Its original photographic operation was supported by the National Geographic Society–Palomar Observatory Sky Survey, a collaboration that produced the iconic POSS-I photographic atlas.

Technical specifications

The instrument is a classic Schmidt camera with an exceptionally fast optical system. It has a 48-inch (1.22-meter) diameter correcting lens and a 72-inch (1.83-meter) spherical primary mirror, yielding a focal ratio of f/2.5. This design provides a very wide, flat field of view of over 6.5 square degrees, ideal for surveying large swaths of the celestial sphere. The telescope utilizes an equatorial mount housed in a distinctive sliding-roof building. For most of its operational life, it used large-format glass photographic plates, but it was later upgraded with modern CCD detectors. Its location at Palomar Observatory, at an elevation of approximately 1,700 meters, offers favorable seeing conditions for the Northern Hemisphere.

Scientific discoveries and research

The telescope has been instrumental in countless discoveries since the 1950s. The original Palomar Observatory Sky Survey provided the foundational atlas that led to the identification of numerous quasars, asteroids, and distant galaxies. It played a key role in the discovery of Sedna and other trans-Neptunian objects in the Kuiper belt. The Near-Earth Asteroid Tracking program used it to discover thousands of minor planets, including many potentially hazardous asteroids. Its deep, wide-field images have been critical for studies of large-scale structure of the universe, gravitational lensing, and the cosmic distance ladder. Data from its surveys have also been used to discover variable stars and planetary nebulae.

Instrumentation and upgrades

The telescope's primary instrumentation has evolved significantly. For its first four decades, it exclusively used blue-sensitive and red-sensitive photographic emulsions on 14-inch square glass plates. A major upgrade in 1987 installed a three-element correcting lens to improve image quality. The most transformative change occurred in 2001 with the installation of the Palomar QUEST camera, a large mosaic of 112 CCDs, converting the telescope to a fully digital survey instrument. Later, the Zwicky Transient Facility camera, with its wider field and faster readout, was installed, enabling the discovery of supernovae and other transient astronomical phenomena in near real-time.

Role in astronomical surveys

The defining role of the Samuel Oschin telescope has been conducting monumental, systematic sky surveys. It began with the first Palomar Observatory Sky Survey in the 1950s, which mapped the northern sky to a then-unprecedented depth. The second Palomar Observatory Sky Survey in the 1980s and 1990s provided deeper, multi-color data. In the digital era, the Palomar-QUEST survey continued this legacy. Its most prominent modern survey is the Zwicky Transient Facility, which scans the entire visible northern sky every night, feeding data to alert networks like the Astronomical Telegram and catalogs such as the Minor Planet Center. These surveys provide essential data for projects like the Sloan Digital Sky Survey and missions including the Hubble Space Telescope and the James Webb Space Telescope.

Category:Schmidt cameras Category:Palomar Observatory Category:Astronomical surveys Category:Telescopes in the United States