Photometer, "Red Cold Box", 1.3-m Telescope, Kitt Peak Observatory

This temperature controlled insulated container, or "Cold Box" was used to house photoelectric photomultipliers used with telescopes at the Kitt Peak National Observatory (KPNO). The photoelectric photometer is a device for measuring the amount of light gathered by a telescope from point-like sources such as a star or the nucleus of a galaxy. Light collected by a telescope that had then been processed through a diaphragm and filters in the photometer head (Catalogue #A20000791000) was routed onto the face of a photoelectric photomultiplier tube inside the red container. This tube converted the light to an electrical signal and amplified that by a cascade effect. In operation, the box was filled with dry ice to maintain the tube at the low temperature required for enhanced sensitivity and low thermal noise. This box was built at KPNO in 1974 and used extensively for measuring light from astronomical objects; it was donated by the Observatory to NASM in 2000. It is now on display in the Explore the Universe gallery.