Star Observers

US NAVAL OBSERVATORY

http://www.usno.navy.mil/
The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States

Primary missionto produce PNT [Positioning, Navigation and Timing]
()for the United States Navy and the United States Department of Defens

Adde gubernandi studium: Pervenit in astra, et pontum caelo conjunxit
"Increase the study of navigation: it arrives in the stars, and marries the sea with heaven"

The author of Astronomica is neither quoted nor mentioned by any ancient writer.
https://en.wikipedia.org/wiki/Marcus_Manilius

TIME MASTERS
The U.S. Naval Observatory operates two Master Clock facilities.
The primary master clock, in Washington, D.C.
The alternate master clock, at Schriever Air Force Base
maintains
57 HP/Agilent/Symmetricom 5071A-001 high performance cesium atomic clocks and 24 hydrogen masers.
maintains
12 cesium clocks and 3 masers.
maintains
The observatory also operates
4 rubidium atomic fountain clocks, which have a stability reaching 7×10−16