By Alyson Smith
Saturday, July 20th, was the 50th anniversary of the Apollo 11 moon landing, which made it a fitting day for SANDSWA members to tour the historic Hale Telescope at the Palomar Observatory in the Cleveland National Forest, some 60 miles northeast of San Diego. Our guide, Thomas Murphy of UCSD’s Center for Astrophysics and Space Sciences, spent many nights at the observatory during his physics PhD at Caltech.
After a short walk through the beautiful evergreen forest atop Palomar Mountain (elevation 5,600 feet), we spotted the gleaming white dome that houses the telescope–a 330-ton marvel of engineering. To make such a massive instrument operational, the scope’s designers suspended it on a thin layer of oil to reduce friction and invented an apparatus that would allow it to deform under its own weight without misaligning the optics.
The star of the show is the 200-inch parabolic mirror. When the Hale scope first saw light in 1949, its mirror was twice as large as the most advanced telescope of its time. Cast out of Pyrex–a material known for withstanding large temperature changes without distorting or cracking–the glass has a honeycomb of hollow cavities to decrease its weight and increase its resilience. It holds a very thin layer of aluminum in the perfect parabolic shape to capture the faint light of distant stars, supernovae, and galaxies.
The scope’s support structures hid much of the machinery (including the mirror) from view, and preparations for that night’s observations prevented us from getting too close. Luckily for us, drawings by artist Russel Porter lined the halls of the observatory, displaying the inner workings of different parts of the telescope. Murphy referenced these drawings, which Porter sketched entirely from blueprints, to teach us how the telescope works.
In its 70 years of use, the Hale telescope has enabled ground-breaking discoveries, including quasars and the acceleration of the universe. The feats of science and engineering that made it possible continue to inspire efforts to build larger telescopes and push the limits of humanity’s view of the universe.
For more information about the history of the Hale telescope, check out The Perfect Machine by Ronald Florence.