× 0. Palomar Observatory
M. Visitor Center (Museum)
H. Hale Dome

Building Palomar Observatory

Palomar Observatory is among the most iconic scientific facilities in the world, and a crown jewel in the research traditions of Caltech. Conceived of nearly 100 years ago, the observatory has been in continuous scientific operation since the mid-30s, and remains productive and relevant today. Palomar is most directly the vision of George Ellery Hale (1868–1938). In a tour-de-force effort framed by the challenges of the Great Depression and the Second World War, Hale and a dedicated group of astronomers, engineers, technicians, and builders secured funding, designed the telescopes and site, and created the observatory in much the same state as it exists today.


The Rockefeller Foundation awarded the grant that funded Palomar Observatory construction in 1928. By the end of that year George Ellery Hale, for whom the Palomar 200-inch telescope is named, was already assembling the consortium of engineers, scientists, and industrial associates that would build the observatory and its flagship telescopes over the next twenty years.

Concept development and prototyping for the 200-inch telescope was already well underway by mid-1929. Determined to improve on the 100-inch Hooker Telescope design, the observatory team in conjunction with General Electric initially pursued fused quartz as a material for the 200-inch primary mirror. The fused quartz experiment failed; working with the challenging material at the scale of the primary mirror was beyond 1930s technology. But the collaboration with General Electric set the pattern for subsequent involvement of prominent industrial partners. Corning Glass Works succeeded in fabricating a 200-inch Pyrex blank. Westinghouse, a prominent US Navy contractor, was enlisted to create the enormous steel structure of the telescope. Consolidated Steel Corporation built the massive Hale Telescope dome. In many aspects the observatory was a sufficiently ambitious advance over existing telescopes that new technologies were required to make it feasible. A highly collaborative and geographically diverse consortium solved the many technical challenges; important contributions to engineering design, development, and fabrication were made both in Pasadena and among the industrial partners across the country.

Design and construction of the observatory and its telescopes all happened against the backdrop of the Great Depression. Global business activity contraction and economic hardship made life difficult for many, but the conditions also worked to project advantage. With so many Americans looking for work, labor for Palomar site construction was plentiful and relatively inexpensive. With other opportunities curtailed, businesses large and small were enthusiastic to be seen supporting the high-profile project. Companies promoting themselves in association with the new facility only served to raise Palomar’s profile among a public hungry for good news. By 1940 the observatory’s main structures and 200-inch telescope mount were complete and initial operations seemed imminent.

This positive arc continued until the US entry into World War II. Suddenly public focus shifted to the war effort and the perceived vulnerability of the West Coast to enemy attack. As observatory team members were assigned elsewhere, work on the last remaining large component—the 200-inch primary mirror—was suspended, and the invaluable mirror asset was secured to protect it from possible wartime damage. Observatory development remained in stasis for the four years of US engagement in World War II. By the beginning of 1946 most of the core team was back to work on completing the 200-inch mirror, and by late 1947 the mirror arrived at Palomar for final figuring and integration into the waiting telescope structure.

Palomar is perhaps unique among scientific facilities in its broad integration into the public consciousness of its time, and has been compared to the Apollo program in cultural impact. The observatory was developed during a time of adversity that made its aspirational aims a hopeful message to many, and businesses saw their self-interests aligned with promoting that message. That the observatory was sited in Southern California—a prominent nexus of the entertainment industry and technical innovation—seemed a natural fit. By the time scientific observations began in 1949 the Hale Telescope had become an international icon of human aspiration, ingenuity, and curiosity among those anxious to see what new insights it might provide.

Upcoming guided tour.