Palomar Observatory is owned and operated by the California Institute of Technology, a privately endowed educational and research institution located in Pasadena, California, and is used to support the scientific research programs of Caltech's faculty and students.

The principal instruments at Palomar are the 200-inch Hale Telescope, the 48-inch Samuel Oschin Telescope, the 18-inch Schmidt telescope, and the 60-inch reflecting telescope. By agreement, Caltech shares use of the Hale Telescope with astronomers from Cornell University and the Jet Propulsion Laboratory.

• The History
• Scientific research
• Telescope Animations Light path - Telescope Motion - Dome Rotation
• Virtual Tour : Visit the 200" prime focus cage with Jesse Greenstein
• Light Pollution

Meanwhile, at the Corning Glass Works in New York State, techniques were being developed that ultimately led to the successful casting of the 200-inch Pyrex glass disk on December 2, 1934. After a cooling period of eight months, the 20-ton disk was shipped by rail to Pasadena for the long process of grinding and polishing that would transform it to the precise shape and size required for astronomical observations.

Construction of the building to house the 200-inch (including the 1000-ton rotating dome) and the telescope structure (the moving parts weigh about 530 tons) began in the mid-1930s and was nearly complete by 1941 when the United States entered World War II. But the war delayed polishing of the mirror, and it was not until November 18, 1947, that the finished mirror, now weighing only 14.5 tons, began its two-day trip to Palomar Mountain where it was installed in the telescope for a period of testing and adjustment.

Scientific research at Palomar Observatory since 1948 has been remarkably productive. The Hale Telescope has been used on virtually every clear night to provide astronomers with the information they need to pursue their investigations. The scope of this work ranges from studies of asteroids and comets within the solar system, to the stars that comprise our Milky Way Galaxy, out to the uncounted galaxies beyond our own, and finally to the quasars -- beacons in the universe so distant that the light collected from them with the Palomar telescopes has been billions of years in transit to the Earth.

By careful study of the light from these celestial objects, astronomers hope to extend our understanding of the universe. How did the Sun and planets form? How do stars form, evolve, and die? How old is the Milky Way? How old is the universe? How did it form, and what is its fate? The telescopes at Palomar Observatory are the tools astronomers need to answer these and other similar questions about the universe.

These tools are constantly being improved. Within the past several years, for example, the 200-inch telescope has been equipped with sensitive position sensors and high-speed computers -- modifications that greatly improve the efficiency of its operation. Even more significant is the development of new electronic devices that sense faint signals of light from distant celestial objects. Some of these devices are 100 times more sensitive than the photographic plates used when the telescope first went into service. Others are able to measure infrared light, a part of the spectrum that was inaccessible to astronomers in 1948. Because of these improvements, the 200-inch Hale Telescope can now be used to attack research problems that would have been impossible just a few years ago.

It is only recently that the wide-field 48-inch Samuel Oschin Telescope converted to digital imaging. The telescope, which can be thought of as a camera, formerly used glass photographic plates 14 inches square to record an image of the sky. It is currently outfitted with an array of 112 electronic light-sensitive chips known as charged coupled devices (CCDs). This new array of CCDs makes the Samuel Oschin Telescope a 161-megapixel camera. Current investigations range from the search for asteroids that might threaten our Earth to searches for quasars at the edge of the universe.

Much of the light radiated by the stars, galaxies, and quasars is at wavelengths that are absorbed by the atmosphere of the Earth. To collect this light, astronomers are now able to operate highly specialized telescopes that orbit the Earth above the atmosphere. The relationship between these space telescopes and those at ground-based observatories like Palomar is complementary. Neither space-based nor ground-based observatories can accomplish alone what they can working in concert.

Light pollution is an increasing problem for observatories everywhere. One of the reasons Palomar Mountain was selected as the site for the 200-inch telescope was its dark skies that would allow observation of the faintest galaxies without the interference of city lights. Since 1934, rapid urbanization of southern California has resulted in a significant increase in the amount of sky glow. If such light pollution continues to increase, it will seriously reduce the effectiveness of the Palomar Observatory. Fortunately, steps can be taken to minimize those effects. These include:

• Using the minimum amount of outdoor lighting required for the task.
• Shielding lights to prevent any direct upward illumination.
• Turning lights off when they are not needed.
• Using low-pressure sodium lights wherever possible because these lights cause the least interference with the observatory.

For more information on how light pollution affects Palomar Click Here.