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.

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OUR CONTENT FROM THE UNITED STATES NAVAL OBSERVATORY

Transit of Venus (1882)

The etching above shows William Crabtree in 1639 making what is thought to be one of the very first observations of the ‘Transit of Venus’, …Continued