Longines Sidereal Second-Setting watch

Longines Sidereal Second-Setting watch
Before 1927, watches used with sextants for celestial sightings could only be set to the minute. A watch error of 30 seconds caused a navigational error of up to 12 kilometers (7 miles). In 1927, P. V. H. Weems devised a watch with an adjustable second hand that could be set using radio time signals. This was one of his personal navigation watches.  Sidereal refers to the watch running on a celestial day (about 23 hours, 56 minutes), rather than the 24 hour solar day. This object will be part of the Time and Navigation exhibit opening in April 2013.
  • WEB12700-2013

  • Copyright/Owner: Smithsonian Institution
  • Photographer: Mark Avino
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