This is one of two four-sided pyramidal mirrors used on the Hale 200-inch telescope at the Cassegrain focus to split the light from the telescope into four beams and send these into an instrument called the 4-shooter. "4 Shooter" is an array of four CCD-based cameras built as a proof test of the split field concept design for the Wide Field/Planetary camera of the Hubble Space Telescope. This design was developed specifically to overcome the intrinsic limitations of early CCD chips that were inherently small, and thus could not cover useful areas of the sky at the scale created by large long-focus telescopes. The NASM collection holds the complete, working camera, including split field optics and 2 of the original 4 CCD camera units that were used programmatically on the 200-inch for many years and featured in Richard Preston's "First Light" as a galaxy and quasar finder. The 4-shooter was donated to the Museum by the California Institute of Technology in September 1999.