Palomar Observatory

Astronomer George Ellery Hale, whose vision created the Palomar Observatory, built the world's largest telescope four times in succession.[8] He published an article proposing what was to become the 200-inch Palomar reflector; it was an invitation to the American public to learn about how large telescopes could help answer questions relating to the fundamental nature of the universe. Hale hoped that the American people would understand and support his project even though the country was in the depths of the Great Depression.

Hale followed this article with a letter to the International Education Board (later absorbed into the General Education Board) of the Rockefeller Foundation dated April 16, 1928 in which he requested funding for this project. In his letter, Hale stated:

"No method of advancing science is so productive as the development of new and more powerful instruments and methods of research. A larger telescope would not only furnish the necessary gain in light space-penetration and photographic resolving power, but permit the application of ideas and devices derived chiefly from the recent fundamental advances in physics and chemistry."

The 200-inch telescope is named after astronomer and telescope builder George Ellery Hale. It was built by Caltech with a $6 million grant from the Rockefeller Foundation, using a Pyrex blank manufactured by Corning Glass Works under the direction of George McCauley after several years of unsuccessful attempts by General Electric under Dr. A.L. Ellis. The first steps toward funding the construction of the 200 inch telescope were taken by Hale in 1928 and included a 23-ton glass block cast by José Antonio de Artigas Sanz. Dr. J.A. Anderson was the initial project manager, assigned in the early 1940s.[9] The telescope (the largest in the world at that time) saw first light January 26, 1949 targeting NGC 2261.[10] The American astronomer Edwin Powell Hubble was the first astronomer to use the telescope.

The 200-inch telescope was the largest telescope in the world from 1949 until 1975, when the Russian BTA-6 telescope saw first light. Astronomers using the Hale Telescope have discovered distant objects at the edges of the known universe called quasars and have given us the first direct evidence of stars in distant galaxies. They have studied the structure and chemistry of intergalactic clouds, leading to an understanding of the synthesis of elements in the universe, and have discovered thousands of asteroids. A one-tenth-scale engineering model of the telescope at Corning Community College in Corning, New York, home of the Corning Glass Works (now Corning Incorporated), was used to discover at least one minor planet, 34419 Corning.†

Hale Telescope Dome

According to the Observatory's Public Affairs Office, Russell W. Porter was primarily responsible for the Art Deco architecture of the Observatory's buildings, including the dome of the 200-inch Hale Telescope. Porter was also responsible for much of the technical design of the Hale Telescope and Schmidt Cameras, producing a series of cross-section engineering drawings. Porter worked on the designs in collaboration with many engineers and Caltech committee members.[11][12][13]

Max Mason directed the construction and Theodore von Karman was involved in the engineering.

• Ira Sprague Bowen, 1948–1964
• Horace Welcome Babcock, 1964–1978
• Maarten Schmidt, 1978–1980
• Gerry Neugebauer, 1980–1994
• James Westphal, 1994–1997
• Wallace Leslie William Sargent, 1997–2000
• Richard Ellis, 2000–2006
• Shrinivas Kulkarni, 2006–2018
• Jonas Zmuidzinas, 2018–

Much of the surrounding region of Southern California has adopted shielded lighting to reduce the light pollution that would potentially affect the observatory.[14]

• An 18-inch Schmidt camera became the first operational telescope at the Palomar in 1936. In the 1930s, Fritz Zwicky, a Caltech astronomer, discovered over 100 supernovae in other galaxies with this telescope and gathered the first evidence for dark matter. Comet Shoemaker-Levy 9 was discovered with this instrument in 1993. It has since been decommissioned and is on display at the small museum/visitor center.[22][23]
• The Palomar Testbed Interferometer was a multi-telescope instrument that permitted astronomers to make very high resolution measurements of the sizes and positions of objects in space. The shapes of some bright stars were measured with the PTI. It operated from 1995 to 2008.[24]
• The Palomar Planet Search Telescope (PPST), also known as Sleuth, was a 0.1 m (3.9 in) robotic telescope that operated from 2003 until 2008. It was dedicated to the search for planets around other stars using the transit method. It operated in conjunction with telescopes at Lowell Observatory and in the Canary Islands as part of the Trans-Atlantic Exoplanet Survey (TrES).[25]

The initial Palomar Observatory Sky Survey (POSS or POSS-I), sponsored by the National Geographic Institute, was completed in 1958. The first plates were shot in November 1948 and the last in April 1958. This survey was performed using 14 inch² (6 degree²) blue-sensitive (Kodak 103a-O) and red-sensitive (Kodak 103a-E) photographic plates on the 48-inch Samuel Oschin Schmidt reflecting telescope. The survey covered the sky from a declination of +90 degrees (celestial north pole) to −27 degrees and all right ascensions and had a sensitivity to +22 magnitudes (about 1 million times fainter than the limit of human vision). A southern extension extending the sky coverage of the POSS to −33 degrees declination was shot in 1957–1958. The final POSS I consisted of 937 plate pairs.

Fritz Zwicky was the first astronomer to observe on Palomar Mountain and was the father of the sky survey technique.[27]

Digitized Sky Survey (DSS) produced images which were based on the photographic data developed in the course of POSS-I.[28]

J.B. Whiteoak, an Australian radio astronomer, used the same instrument to broaden this POSS-I data further. Whiteoak's observations extended south to about −45 degrees declination, using the same field centers as the corresponding northern declination zones. Unlike POSS-I, the Whiteoak extension consisted only of red-sensitive (Kodak 103a-E) photographic plates.

The Second Palomar Observatory Sky Survey (POSS II, sometimes Second Palomar Sky Survey) was performed in the 1980s and 1990s and made use of better, faster films and an upgraded telescope. The Oschin Schmidt was given an achromatic corrector and provisions for autoguiding. Images were recorded in three wavelengths: blue (IIIaJ), red (IIIaF) and near infrared (IVN) plates, respectively. Observers on POSS II included C. Brewer, D. Griffiths, W. McKinley, J. Dave Mendenhall, K. Rykoski, Jeffrey L. Phinney and Jean Mueller (who discovered over 100 supernovae by comparing the POSS I and POSS II plates). Mueller also discovered several comets and minor planets during the course of POSS II, and the bright Comet Wilson 1986 was discovered by then graduate student C. Wilson early in the survey.[29]

Until the completion of the Two Micron All Sky Survey (2MASS), POSS II was the most extensive wide-field sky survey. When completed, the Sloan Digital Sky Survey will surpass POSS I and POSS II in depth, although the POSS covers almost 2.5 times more area on the sky.

POSS II also exists in digitized form (i.e., the photographic plates were scanned) as part of the Digitized Sky Survey (DSS).[30]

The multi-year POSS projects were followed by the Palomar Quasar Equatorial Survey Team (QUEST) Variability survey.[31] This survey yielded results that were used by several projects, including the Near-Earth Asteroid Tracking project. Another program that used the QUEST results discovered 90377 Sedna on 14 November 2003, and around 40 Kuiper belt objects. Other programs that share the camera are Shri Kulkarni's search for gamma-ray bursts (this takes advantage of the automated telescope's ability to react as soon as a burst is seen and take a series of snapshots of the fading burst), Richard Ellis's search for supernovae to test whether the universe's expansion is accelerating or not, and S. George Djorgovski's quasar search.

The camera for the Palomar QUEST Survey was a mosaic of 112 charge-coupled devices (CCDs) covering the whole (4 degree by 4 degree) field of view of the Schmidt telescope. At the time it was built, it was the largest CCD mosaic used in an astronomical camera. This instrument was used to produce The Big Picture, the largest astronomical photograph ever produced.[32] The Big Picture is on display at Griffith Observatory.

Current research programs on the 200-inch Hale Telescope cover the range of the observable universe, including studies on near-Earth asteroids, outer solar system planets, Kuiper Belt objects, star formation, exoplanets,[33] gamma-ray bursts, black holes, and quasars.[34]

The 48-inch Samuel Oschin Schmidt Telescope operates robotically, and supports a new transient astronomy sky survey, the Zwicky Transient Facility (ZTF).[35]

The 60-inch telescope operates robotically, and supports ZTF by providing rapid, low-dispersion optical spectra for initial transient detection classification using the for-purpose Spectral Energy Distribution Machine (SEDM)[36] integral-field spectrograph.

In September 2007, a team of astronomers from the United States and Britain released some of the clearest pictures ever taken of the sky. The pictures were obtained through the use of a new hybrid "lucky imaging" and adaptive optics system that sharpens pictures taken from the Palomar Observatory. The resolution attained exceeds that of the Hubble Space Telescope by a factor of two.[37]