The "Great Equatorial" was completed in 1873 at a cost of just over $46,000. It was installed at USNO's Foggy Bottom site in Washington, DC. Built by the firm of Alvan Clark & Sons, it was the largest refractor telescope in the world for nearly decade. Re-located to the USNO's present site in 1893, the venerable telescope is still used every clear night for measuring the astrometric properties of double stars.