NPOI can record images of stars and optically separate distant pairs of stars so close together that
they appear as a single star in even the largest conventional telescopes.
The NPOI has the ability to measure the precise relative positions of stars across the sky which the Naval Observatory uses as a reference system for the determination of
positions on earth and in space and for monitoring time keeping. Currently operating at about one-fourth of its designed capability, when finished the interferometer will span
the distance of over four football field lengths, 430 meters.
[See NPOI Website]