2.2 Micron Telescope, Infrared, Caltech

This is the original infrared reflecting telescope built at the California Institute of Technology in the early 1960s to survey the sky for infrared radiation sources. Its 1.6-meter (62-inch) parabolic mirror was made using a novel technique now called spin casting. Epoxy resin was poured onto a rapidly rotating dish and spun into a perfectly parabolic shape as it hardened. After the resin hardened, the surface was vacuum coated with aluminum to provide a reflective surface. Installed at Mount Wilson Observatory as well as at other high-altitude sites, the telescope was used to create the first 2.2-micron all-sky survey. It resulted in a catalogue of thousands of infrared sources that demonstrated that this spectral range was a viable new field for investigation.

Photoelectric data were collected from a set of PbS photoconductive tubes mounted at the apex of the triangular frame above the mirror. These were continuous brightness records collected as the sky moved past the field of view of the instrument, mounted typically to see the meridian. These records were read out and recorded on paper strip charts and then inspected to locate infrared sources. It was donated to NASM by Caltech in 1982, and displayed in the "Stars" gallery until 1997. It is now displayed at the museum's Udvar Hazy Center.

Caltech Infrared Telescope