Press Release

Caltech and ESO Join Forces to Produce Sky Atlas

26 January 1990

The California Institute of Technology (Caltech) of Pasadena, California, U.S.A. and the European Southern Observatory have concluded an agreement by which ESO will undertake the responsibility of producing high-quality copies of photographic sky survey plates obtained with the Palomar 40-inch Oschin Telescope and to distribute the resulting photographic atlas [1].

The second Palomar Observatory Sky Survey is a mammoth decade-long project to photograph the entire northern sky using sensitive new photographic techniques. The new atlas of the heavens, contained on 2,682 glass plates or film transparencies, will serve as the basic astronomical guide to the northern skies for decades to come. It will be known as the Palomar Observatory - European Southern Observatory Atlas of the Northern Sky.

“We are delighted that ESO will be copying and distributing the results of the Palomar Sky Survey'', says Robert J. Brucato, assistant director of Palomar Obervatory. “ESO has considerable experience from their work on the southern sky surveys conducted by ESO and by the United Kingdom Schmidt Telescope in Australia and the results were excellent. We had been planning on doing the copying and distributing at Caltech, but we decided to have the work done at ESO in the interest of making high-quality copies available to the astronomical community at the minimum price possible''.

The photographic work at ESO will be carried out by a team of experienced photographers, headed by staff astronomer Richard M. West. The laboratory employs highly specialized techniques, many of which were invented at ESO, and which guarantee a minimal loss of information in the copying process. The laboratory staff has more than 15 years of practice with survey and atlas work in the southern sky. Comments the ESO astronomer: “Our laboratory facilities and copying methods are unique in the astronomical world and we have until now produced more than 300,000 absolutely faithful photographic copies of large Schmidt telescope plates. Each original plate exposed at the telescope contains several millions of images of stars and galaxies and we do not want to remove any real images or add any false images during the copying process.''

Able to record celestial objects several million times fainter than can be detected with the naked eye, the plates of the Palomar Sky Survey will become a standard reference in the libraries of every major observatory around the world. Astronomers will use the data from the new survey to:

  • discover new quasars, galaxies, stars, asteroids and comets;
  • map the structure and circulation of our Milky Way galaxy by comparing the positions of stars with those in the last major survey 30 years ago;
  • serve as a celestial road map for the NASA/ESA Hubble Space Telescope, scheduled for launch on the Space Shuttle this year; the joint ESA/ESO European Coordinating Facility for the HST is located at the ESO Headquarters in Garching;
  • identify at visible and near-infrared wavelengths, objects discovered with telescopes that see in the radio, x-ray, or infrared regions of the spectrum.

The multi-million dollar Palomar Observatory Sky Survey is funded by grants from the Eastman Kodak Company, the National Geographic Society, the Samuel Oschin Foundation, and the Alfred Sloan Foundation, with additional funding from NASA and the National Science Foundation. Begun in 1986, the survey is scheduled for completion in the mid-1990s. ESO expects to terminate the copying a few years later, having then distributed the entire atlas to astronomical institutes all over the world.

Caltech took its first step in the business of sky surveys in 1948, when Institute astronomers and technicians began the eight-year task of mapping the northern sky for the first Palomar Sky Survey. This proved to be one of the most important developments in 20th century astronomy, because it provided astronomers with an unprecedented wealth of information about the heavens. ESO carried out similar surveys of the southern sky after the erection of the ESO Schmidt telescope at La Silla, in 1972. Part of this work was done in collaboration with the UK Schmidt telescope in Australia.

In 1980, Caltech astronomers began planning for a new, northern survey because of advances in photographic and telescope technology and the changes in the heavens over the ensuing three decades. The Oschin Telescope was substantially refurbished before the second sky survey was begun. This included a new, $380,000 lens that enables the telescope to focus a wide range of wavelengths. In addition, advances in photographic technology have led to the development of photographic plates that are far more sensitive than those available in 1948.

Each glass plate is 14 inches square, and photographs a segment of the sky about 6.5 degrees across, about 13 times the diameter of the full moon. It would take 894 such segments to cover the entire northern hemisphere of the sky, but since each segment is photographed at three wavelengths, the survey will finally comprise 2,682 plates. Because of the trails of overflying airplanes, plate defects, or other observational problems, the Caltech astronomers expect that they will have to expose two plates for every one that is finally accepted for the survey.


[1] Caltech issues simultaneously a Press Release about this collaboration.


Richard West
Garching, Germany
Tel: +49 89 3200 6276

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About the Release

Release No.:eso9002
Legacy ID:PR 02/90
Name:European Southern Observatory
Type:Unspecified : Technology : Observatory