Burrell Schmidt telescope

Burrell Schmidt telescope. A wide-field astrograph of the Schmidt camera design, it was constructed in the late 1940s through a bequest from Cleveland industrialist Cyrus B. Burrell. Originally installed at the Warner and Swasey Observatory near Cleveland, Ohio, the instrument was renowned for its pioneering contributions to extragalactic astronomy and nebulae studies before its relocation to a premier national facility. Its unique optical design and historical significance have made it a valuable tool for large-scale sky surveys over many decades.

History and construction

The genesis of the instrument traces to a generous bequest by philanthropist Cyrus B. Burrell, intended to advance astronomical research at Case Institute of Technology. Commissioned in 1946, the telescope was engineered and built by the precision instrument firm Warner and Swasey Company, which also operated its original home, the Warner and Swasey Observatory. Under the directorship of astronomer Jason John Nassau, it became operational in 1947, representing one of the largest and most advanced Schmidt cameras in North America at the time. For over two decades, it served as a primary research instrument for the Cleveland astronomical community, conducting systematic observations of the Milky Way and distant galaxies despite the challenges of light pollution from the growing city.

Design and specifications

The telescope employs the classic Schmidt camera optical configuration, which uses a spherical primary mirror paired with a thin, aspheric correcting plate at the entrance to eliminate spherical aberration and provide a wide, flat field of view. Its optics consist of a 0.91-meter (36-inch) diameter spherical mirror and a 0.61-meter (24-inch) correcting plate, yielding a fast focal ratio of f/1.75 and a focal length of 1.07 meters. This design enables it to photograph large areas of the celestial sphere on a single photographic plate, with a field of view exceeding 6 degrees. The original instrument utilized glass photographic plates as detectors, which were later replaced by modern CCD cameras. Its compact, sealed tube design minimizes internal air currents and protects the optics, a hallmark of the Schmidt camera architecture perfected by Bernhard Schmidt.

Scientific contributions

During its early years at Warner and Swasey Observatory, the telescope produced foundational atlases of the Milky Way, notably the Nassau Galactic Atlas. Under Jason John Nassau and colleague Patricia T. Garmany, it was instrumental in cataloging planetary nebulae and studying the distribution of OB stars and H II regions. A major program led by astronomer William W. Morgan used the telescope's wide-field capability to map the spiral structure of our galaxy through observations of OB associations. Its deep sky surveys also contributed to the identification of quasar fields and studies of galaxy clusters. The instrument's photographic archives, spanning decades, remain a valuable resource for studying long-term variability in stellar objects and nebulae.

Location and operation

In 1979, seeking darker skies to remain competitive, the telescope was moved from Ohio to the Kitt Peak National Observatory in Arizona, a site operated by the NOAO. The relocation to the summit of Kitt Peak placed it among world-class facilities like the Mayall Telescope and the WIYN Observatory, dramatically improving its observational efficiency. At this premier site, it has been operated primarily by Case Western Reserve University for dedicated research programs. The telescope is used for both targeted investigator-led projects and large-scale, systematic surveys, benefiting from the exceptional seeing conditions and low humidity of the Sonoran Desert.

Upgrades and modifications

The most significant modernization occurred after the move to Kitt Peak National Observatory, with the replacement of the original photographic plate system with a series of electronic CCD detectors. This transition greatly increased its sensitivity and enabled digital data acquisition. Further upgrades included the installation of new filter wheels to facilitate multi-color photometry and the implementation of automated control systems. In the 21st century, it has been equipped with large-format CCD mosaics, allowing it to participate in contemporary sky survey projects such as the Local Volume Legacy Survey. These continual upgrades have preserved the utility of this historic instrument, allowing it to contribute to modern astrophysical research on dark matter, galaxy evolution, and transient events.

Category:Schmidt cameras Category:Telescopes in the United States Category:Case Western Reserve University Category:Kitt Peak National Observatory