Palomar Observatory


The Palomar Observatory is an astronomical research observatory in the Palomar Mountains of San Diego County, California, United States. It is owned and operated by the California Institute of Technology. Research time at the observatory is granted to Caltech and its research partners, which include the Jet Propulsion Laboratory, Yale University, and the National Astronomical Observatories of China.
The observatory operates several telescopes, including the Hale Telescope, the Samuel Oschin telescope, the Palomar Telescope, and the Gattini-IR telescope. Decommissioned instruments include the Palomar Testbed Interferometer and the first telescopes at the observatory, an Schmidt camera from 1936.

History

Hale's vision for large telescopes and Palomar Observatory

Astronomer George Ellery Hale, whose vision created Palomar Observatory, built the world's largest telescope four times in succession. He published a 1928 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 followed this article with a letter to the International 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."

Hale Telescope

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. Dr. J.A. Anderson was the initial project manager, assigned in the early 1930s. The telescope saw first light January 26, 1949, targeting NGC 2261. 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 quasars at cosmological distances. They have studied the chemistry of stellar populations, leading to an understanding of the stellar nucleosynthesis as to origin of elements in the universe in their observed abundances, 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, was used to discover at least one minor planet, 34419 Corning.

Architecture and design

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

Directors

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

Telescopes and instruments

  • The Hale Telescope was first proposed in 1928 and has been operational since 1949. It was the largest telescope in the world for 26 years.
  • A reflecting telescope is located in the Oscar Mayer Building, and operates fully robotically. The telescope became operational in 1970, and was built to increase sky access for Palomar astronomers. Among its notable accomplishments is the discovery of the first brown dwarf. The 60-inch telescope currently hosts the SED Machine integral field spectrograph instrument used as part of ZTF transient followup and classification.
  • The Samuel Oschin telescope development began in 1938, and the telescope saw first light in 1948. It was initially called the 48-inch Schmidt, and was dedicated to Samuel Oschin in 1986. Among many notable accomplishments, Oschin observations led to the discovery of the important dwarf planets Eris and Sedna. Eris's discovery initiated discussions in the international astronomy community that led to Pluto being re-classified as a dwarf planet in 2006. The Oschin presently operates fully robotically and hosts the 570-million-pixel ZTF Camera —the discovery engine for the ZTF project.
  • The WINTER 1x1-degree reflecting robotic telescope has been operational since 2021. It is dedicated to the seeing-limited time domain survey of the infrared sky, with a particular emphasis on identifying r-process material in binary neutron star merger remnants detected by LIGO. The instrument observes in Y, J, and a short-H band tuned to the long-wave cutoff of the InGaAs sensors, covering a wavelength range from 0.9 to 1.7 microns.

    Decommissioned instruments

  • An Schmidt camera became the first operational telescope at Palomar in 1936. In the 1930s, Fritz Zwicky and Walter Baade advocated adding survey telescopes at Palomar, and the 18-inch was developed to demonstrate the Schmidt concept. Zwicky used the 18-inch to discover over 100 supernovae in other galaxies. 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.
  • The Palomar Testbed Interferometer was a multi-telescope instrument that made high-angular-resolution measurements of the apparent sizes and relative positions of stars. The apparent sizes and in some cases shapes of bright stars were measured with PTI, as well as the apparent orbits of multiple stellar systems. PTI operated from 1995 to 2008.
  • The Palomar Planet Search Telescope, also known as Sleuth, was a 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.

    Research

Palomar Observatory remains an active research facility, operating multiple telescopes every clear night, and supporting a large international community of astronomers who study a broad range of research topics.
The Hale Telescope remains in active research use and operates with a diverse instrument suite of optical and near-infrared spectrometers and imaging cameras at multiple foci. The Hale also operates with a multi-stage, high-order adaptive optics system to provide diffraction-limited imaging in the near-infrared. Key historical science results with the Hale include cosmological measurement of the Hubble flow, the discovery of quasars as the precursor of Active Galactic Nuclei, and studies of stellar populations and stellar nucleosynthesis.
The Oschin and 60-inch telescopes operate robotically and together support a major transient astronomy program, the Zwicky Transient Facility.
The Oschin was created to facilitate astronomical reconnaissance, and has been used in many notable astronomical surveys—among them are:

POSS-I

The initial Palomar Observatory Sky Survey, sponsored by the National Geographic Institute, was completed in 1958. The first plates were exposed in November 1948 and the last in April 1958. This survey was performed using 14-inch2 blue-sensitive and red-sensitive photographic plates on the Oschin Telescope. The survey covered the sky from a declination of +90° to −27° and all right ascensions and had a sensitivity to +22 magnitudes. A southern extension extending the sky coverage of the POSS to −33° declination was shot in 1957–1958. The final POSS I dataset consisted of 937 plate pairs.
The Digitized Sky Survey produced images which were based on the photographic data developed in the course of POSS-I.
J.B. Whiteoak, an Australian radio astronomer, used the same instrument to extend POSS-I data south to −42° declination. Whiteoak's observations used the same field centers as the corresponding northern declination zones. Unlike POSS-I, the Whiteoak extension consisted only of red-sensitive photographic plates.

POSS-II

The Second Palomar Observatory Sky Survey was performed in the 1980s and 1990s and made use of better, faster films and an upgraded telescope. The Oschin Schmidt was upgraded with an achromatic corrector and provisions for autoguiding. Images were recorded in three wavelengths: blue, red, and near-infrared plates. Observers on POSS II included Cynthia Brewer, D. Griffiths, W. McKinley, J. Dave Mendenhall, K. Rykoski, Jeffrey L. Phinney, and Jean Mueller. 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.
Until the completion of the Two Micron All Sky Survey, 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 as part of the Digitized Sky Survey.