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Hale telescope
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The Hale Telescope is the largest telescope at the Palomar Observatory, named after astronomer George Ellery Hale. The , 3.3 telescope was the largest operating telescope in the world from its completion in 1948 until the BTA-6 became operational in 1975. However the BTA-6 had large defects in its mirror, and the resolving power of the Hale, 0.025 arc seconds, was not exceeded until the completion of the Keck 1 telescope in 1993.
Overview
Hale supervised the building of the telescopes at the Mount Wilson Observatory with grants from the Carnegie Institution of Washington: the 60-inch (1.5 m) telescope in 1908 and the 100-inch (2.5 m) telescope in 1917.
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Encyclopedia
The Hale Telescope is the largest telescope at the Palomar Observatory, named after astronomer George Ellery Hale. The , 3.3 telescope was the largest operating telescope in the world from its completion in 1948 until the BTA-6 became operational in 1975. However the BTA-6 had large defects in its mirror, and the resolving power of the Hale, 0.025 arc seconds, was not exceeded until the completion of the Keck 1 telescope in 1993.
Overview
Hale supervised the building of the telescopes at the Mount Wilson Observatory with grants from the Carnegie Institution of Washington: the 60-inch (1.5 m) telescope in 1908 and the 100-inch (2.5 m) telescope in 1917. These telescopes were very successful, leading to the rapid advance in understanding of the scale of the Universe through the 1920s, and demonstrating to visionaries like Hale the need for even larger collectors.
In 1928 Hale secured a grant of US$6 million from the Rockefeller Foundation for "the construction of an observatory, including a reflecting telescope" to be administered by the California Institute of Technology (Caltech), of which Hale was a founding member. In the early 1930s, Hale selected a site at 1,700 m (5,600 ft) on Palomar Mountain in San Diego County, California, USA as the best site, and less likely to be affected by the growing light pollution problem in urban centers like Los Angeles. The Corning Glass Works was assigned the task of making a mirror out of a new glass blend called Pyrex. Construction of the observatory facilities and dome started in 1936, but because of interruptions caused by World War II, the telescope was not completed until 1948.
The 200-inch Hale saw first light January 26, 1949, targeting NGC 2261. under the direction of American astronomer Edwin Powell Hubble. These were published in the May 7th 1949 issue of Collier's Magazine.
It continues to be used every clear night for scientific research by astronomers from Caltech and their operating partners, Cornell University, the University of California, and the Jet Propulsion Laboratory. It is equipped with modern optical and infrared array imagers, spectrographs, and an adaptive optics system. It has also used Lucky cam, which, in combination with adaptive optics pushed the mirror close to its theoretical resolution for certain types of viewing.
200 inch (5.08 meter) mirror
The mirror planned by George Ellery Hale was cast Corning Glass Works in New York State out of Corngings new Pyrex glass in 1934. After cooling several months it was transported by rail to Pasadena, California. In Pasadena it was ground and polished, while work continued on the structure.
It remains among the largest telescope made with mirrors of single pieces of glass. The Hale's 14.5 ton mirror was a major technological achievement of the 20th century, but it is close to the maximum size piece of glass that can be made rigid enough for a telescope mirror. A larger mirror would sag slightly under its own weight as the telescope is rotated to different positions, changing the precision shape of the surface, which must be accurate to within 2 millionths of an inch. The larger telescopes built in recent years use a different mirror design to solve this problem, with either a single thin mirror or a cluster of smaller flexible mirrors, whose shapes are actively controlled by a computer servo system built into the support cell.
Mount
The Hale telescope uses a type of telescope mount called a Serrurier truss, then newly invented by Mark U. Serrurier of CalTech in Pasadena in 1935. (see also Equatorial mount)
See also
External links and references
Footnotes
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