Today in Smithsonian History: June 30, 1975

Volunteer satellite trackers in Pretoria, South Africa, for Smithsonian Astrophysical Observatory’s Moonwatch Network, one of more than 100 teams worldwide. Volunteers used the “fence method” of observing the sky. Each observer covered a small, overlapping portion of a specific sky quadrant, and watches for the passage of the satellite in his telescope. The instrument used was the Moonwatch Apogee Scope, a 20 power telescope with a 5-inch objective lens. The Moonwatch teams backed up an optical network of 12 Baker-Nunn tracking cameras. (1965. Photographer unknown, as featured in the Torch, December 1983)