Focal Plane Masks

Courtesy of Fermilab Visual Media
Service

Astronomers at the Apache Point Observatory in New Mexico are using this wide-field telescope to catalog more than 100 million celestial objects across 25 percent of the sky and to record about a million spectra. To capture many spectra at once, a metal plate with 640 precisely positioned holes is placed in the focal plane. An optical fiber plugged into each hole captures the light from a single object and relays it to a spectrograph, which records all 640 spectra at once.

Plug Plate

A robotically controlled system drills 640 holes into a metal plate, each corresponding to the position of an object in one section of the sky. The holes are then plugged with optical fibers (as Richard Kron is doing here) that collect light from the objects and transmit it to the spectrograph.