Part of a suite of components of a backup unit for a diagnostic coronagraph that was used during Skylab to assess contamination in the vicinity of the craft. Routine operations on Skylab such as rocket firings to adjust position and waste dumps resulted in the presence of a cloud of fine particles around the spacecraft. This experiment (T025) was designed to record and measure the amount of light scattering from those contaminants. The data were used to determine the effect of that scattering on the various optical instruments on the Apollo Telescope Mount such as the white light coronagraph. The small coronagraph fitted into the Scientific Airlock to run experiments. An occulting disk on the attached boom was oriented to blot out the solar disk so that only the light scattered from the particulate matter reached the instrument. A slide equipped with seven optical filters was interposed between the image and the camera adapter. Data were recorded on 35mm film using a standard Nikon camera.

The coronagraph was transferred to NASM from NASA's Johnson Manned Space Flight Center in 1981.