US NAVAL OBSERVATORY / SCIENCE PHOTO LIBRARY US NAVAL OBSERVATORY / SCIENCE PHOTO LIBRARY
Time Service at US Naval Observatory. US astronomer William Markowitz (1907-1998) at the US Naval Observatory's printing chronograph which compares simultaneously as many as eight time sources. These are used for all official time signals used in astronomical and navigational calculations. Photographed in around 1935, at the US Naval Observatory, Washington DC, USA.
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