This is an original photometer head that formed part of a semi-automated photoelectric photometer built and used at the Kitt Peak National Observatory in the 1960s. This photometer head contains a series of differently sized apertures and filters that could be positioned in the incoming light beam by computer control making it possible to use the telescope system remotely. Once the light beam was isolated by the entrance aperture and filter, it was sent to a photomultiplier tube in another chamber attached below the box. Various different photomultiplier tubes (visual, infrared, etc) were housed in these "cold boxes." Two examples were acquired with the head: the "Red Box" (Catalogue #20000791001) and the "Oke Box" (Catalogue #20000791002).
The photometer was used on various telescopes at KPNO to measure the intensity of the light gathered from point-like sources such as stars and the nuclei of galaxies. It was donated by the Observatory to NASM in 2000. It is now on display in the Explore the Universe gallery.
Gift of Kitt Peak National Observatory