The USNO websites,,,,, and are undergoing modernization efforts. The expected completion of the work and return of service is estimated as 30 April 2020. Please submit a requirements form to the USNOPAO if the information you are seeking is not accessible via other means.

Simon Newcomb

Simon Newcomb (1835-1909) was an astronomer from 1861-1877 before becoming Superintendent of the Nautical Almanac Office in 1877. He served as Superintendent until 1897. During this time he undertook numerous studies in celestial mechanics. His central goal was to place planetary and satellite motions on a completely uniform system, thereby raising solar system studies and the theory of gravitation to a new level. He largely accomplished this goal with the adoption of his new system of astronomical constants at the end of the century. In addition to his technical volumes, Newcomb wrote many popular works, and even a volume of science fiction. Painting by Beverly Stautz
USNO Master Clock Time
Javascript must be Enabled