Perkins Observatory were both growing. Light pollution therefore became increasingly problematic. So in 1961 the Perkins Telescope was moved to Lowell Observatory in Flagstaff, Arizona. Lowell is the largest private observatory (non-university or government affiliated) in the world. Through the end of the 20th century, the Perkins Telescope was the observatory’s largest instrument. Observing time on this instrument was shared between Lowell astronomers and the Ohio State University. The telescope at Perkins was immediately replaced with a cassegrain reflector telescope. It was donated by Michael R. Schottland, an entrepreneur from Martinsville, Virginia. At that time it was the largest privately owned telescope
United States Naval Observatory Flagstaff Station astronomical interferometer of the venerable and proven Michelson Interferometer design. As noted, the majority of interferometric science and operations are funded and managed by NOFS; however, Lowell Observatory and NRL join in the scientific efforts through their fractions of time to use the interferometer; 85% Navy (NOFS and NRL); and 15% Lowell. NPOI is one of the few major instruments globally which can conduct "optical" interferometry. See an illustration of its layout, at bottom. NOFS has used NPOI to conduct a wide and diverse series of scientific studies, beyond just the study of absolute astrometric positions of stars. Additional NOFS