Explore Further: What Was It Like to Work in the Prime Focus Cage?

Astronomer Jesse Greenstein, who spent many years observing with the 200-inch telescope, reminisced about what it was like to work in the prime focus cage: "When the telescope was built, an observer had to ride throughout the night in the prime focus cage to ensure accurate tracking of the telescope. The astronomer ascended to the cage, eighty feet above the floor, in a specially designed elevator.

"A spectrograph in the cage was used to split starlight into its different colors, and a photographic plate recorded the intensity of each color. In this way, each star left its individual 'fingerprint' on the plate. After a careful set-up, when the instruments are ready and the sun is set, the mirror cover opens and another night of observing begins.

"You also had to have a tough bladder because, if possible, if it was a good night, you stayed up from seven o'clock to five. That's ten hours! Working a night in the small cage high above the primary mirror, feeling closer to the stars than to the earth, remains an exhilarating and unforgettable experience."

Back to Menu