CollectionsSource: United States Naval Observatory
United States Naval Observatory
The United States Naval Observatory (USNO) provides a wide range of astronomical data and products, and serves as the official source of time for the U.S. Department of Defense and a standard of time for the entire United States. Their James M. Gilliss Library holds one of the most complete collections of astronomical literature in the world and its digitised content is available through the Naval Oceanography Portal website. (Wikipedia)