Mark III Stellar Interferometer

The Mark III Stellar Interferometer was a long-baseline optical astronomical interferometer, located at the Mount Wilson Observatory, California, United States. It had a maximum baseline of 32 meters and operated in wavelengths between 450 and 800 nm. A joint venture between the United States Naval Observatory, the Naval [Research Laboratory], the Smithsonian Astrophysical Observatory, and the Massachusetts Institute of Technology, it began operation in 1987 and was closed in 1992. The Naval Observatory later constructed a larger interferometer, the Navy Prototype Optical Interferometer.
The Mark III interferometer was used to resolve a number of spectroscopic binary systems, including Alpha Andromedae, Phi Cygni, and many others.