The NPOI does extremely high-resolution astronomy, including precise measurements of stellar positions.
The Navy Precision Optical Interferometer
The NPOI (Navy Precision Optical Interferometer) is a facility of the United States Naval Observatory (USNO) located at Lowell's Anderson Mesa observing site. USNO personnel, collaborators from the Naval Research Laboratory (NRL) use the NPOI for a variety of scientific research programs. Lowell operates the NPOI under contract from the USNO.
Many details about the NPOI are located here, including an online guided tour of the facility.