Palomar Observatory, Home of the 200-Inch Hale Telescope

The dome of the 200-inch Hale Telescope at Palomar Observatory.
The dome of the 200-inch Hale Telescope at Palomar Observatory.

 Coneslayer, CC BY 3.0

Southern California is home to two major observatories, Mount Wilson, north of Los Angeles, and Palomar Observatory, northeast of San Diego. Both were conceived in the late 19th century, built and expanded in the 20th Century, and continue to do cutting-edge astronomy observations in the 21st.

Palomar Observatory, located on Palomar Mountain, is owned and operated by the California Institute of Technology (Caltech) and was started by astronomer George Ellery Hale. He was also the brains behind the Mount Wilson Observatory. Hale was a Caltech founder and was very interested in building ever-larger and more accurate telescopes.

Palomar Observatory Telescopes

  • Palomar Observatory is located northeast of San Diego, California, at the summit of Palomar Mountain.
  • The biggest telescope at Palomar is the 200-inch, 530-ton Hale Telescope. It was named for founder George Ellery Hale.
  • The 48-inch Samuel Oschin Telescope is operated remotely and uses a variety of cameras and instruments. It produces hundreds of images per night in survey mode.
  • The facility's 60-inch telescope came online in 1970 and is remotely operated by astronomers at Caltech.
  • Astronomers have used Palomar telescopes to discover and study everything from exoplanets, Kuiper Belt Objects, and supernovae, to dark matter and distant galaxies.

The 200-Inch Telescope

Palomar is home to one of the largest telescopes in the world, the 200-inch Hale Telescope. Built by Hale with support from the Rockefeller Foundation, the creation of its mirror and building began in the 1920s. The Hale Telescope had its first light in late 1949, and it has been one of the premier instruments for astronomy ever since. It was painstakingly built, and its mirror carefully hauled up the mountain in 1947, just two years before its first light.

The 200-inch Hale Telescope at Palomar Observatory. Caltech/Palomar Observatory

Today, the 200-inch Hale telescope is outfitted with adaptive optics systems that help it capture clear imagery. Astronomers use a Large Format Camera (LFC) to study objects in visible light, as well as a Wide-field Infrared Camera (WIRC) to capture data about distant objects in infrared light. There are also several images available that help astronomers use the telescope to study various cosmic objects over several wavelengths. 

To support such a huge telescope and its instruments, the builders of Palomar Observatory placed it all on a giant stell mount. The whole telescope weighs 530 tons and requires very precise motors for motion. Because southern California is subject to earthquakes, the telescope and its mount rest on piers that are anchored to bedrock some 22 feet below ground. this provides a very stable platform for the very precise observations astronomers need. 

More Palomar Telescopes

The 200-inch wasn't the only telescope built and installed at Palomar. Astronomer Fritz Zwicky used a much smaller 18-inch telescope on the mountain to do his supernova research. That instrument is currently decommissioned. In 1948, the 48-inch Schmidt telescope was put into service and has been used ever since. It has been renamed the Samuel Oschin Schmidt telescope in honor of a southern California entrepreneur who donated money to the observatory. This telescope is also famous for its use in one of the first large photographic sky surveys ever undertaken: the Palomar Observatory/National Geographic Sky Survey (known colloquially as POSS). The plates from that survey are still in use today.

Today, the Oschin telescope is equipped with a state-of-the-art CCD detector and is currently in robotic mode, surveying the skies for a variety of objects. It has been used to study large-scale structures in the universe, to look for dwarf planets, and to detect the sudden flares that herald explosive events such as supernovae, gamma-ray bursts, and outbursts by active galactic nuclei. In the 1970s, Palomar Observatory also opened a 60-inch telescope to astronomers. It was a gift by the Mayer family and is a survey telescope.

The Samuel Oschin Telescope at Palomar Observatory.
The Samuel Oschin Telescope at Palomar Observatory. Scott Roberts, Michael Vergara, Jean Large. CC BY-SA 3.0

Famous Discoveries at Palomar

Over the years, a number of prominent astronomers have made observations using both Mount Wilson's large telescope and Palomar's 200-inch and smaller instruments. They include Edwin P. Hubble, Fritz Zwicky, Allan Sandage, Maarten Schmidt, Eleanor Helin, Vera P. Rubin (who was one of the first women allowed to use the telescope), Gene and Carolyn Shoemaker, and Mike Brown. Between them, these astronomers expanded our view of the universe, looked for evidence of dark matter, tracked comets, and, in an interesting twist of astronomy politics, used the telescope to "downgrade" dwarf planet Pluto. That breakthrough sparked a debate that continues to this day in the planetary science community.

Visiting Palomar Observatory

When possible, Palomar Observatory opens its doors to public visitors, even as it conducts professional research for astronomers. It also maintains a staff of volunteers who help with visitors and represent the observatory at local community events.


  • “Caltech Optical Observatories.” The 48-Inch Samuel Oschin Telescope,
  • “Hale Telescope, Palomar Observatory.” NASA, NASA,
  • The 48-Inch Samuel Oschin Telescope,