The gnomon was a gimbaled rod mounted on a tripod so that the rod was free to point vertically. When deployed on the lunar surface, the shadow cast by the staff indicated sun angle and, therefore, direction. The rod length and the painted scale provided a reference for estimating the sizes of nearby objects. Shades of gray on the rod ranged in reflectivity from 5% to 35% and a color scale enabled more accurate determination of rock and soil colors by comparison. The gnomon configuration was a little different for each Apollo flight. This particular gnomon is similar to the one used on one of the later missions (Apollo 15, 16, or 17) because it has a gray and color scale mounted to one of the tripod legs. The gnomons used on the lunar surface were not returned to Earth.
This object was transferred from NASA to the Smithsonian in 1974.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.