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Weems Watches - WWII And Later


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This is most interesting.




"Longines Sideograph Chronograph

was produced as a very practical pocket-watch, however, the wrist-worn version was produced as a test in March of 1939 and would never leave the vicinity of the Longines firm. While we don’t know the specifics on why it didn’t find its way into production, the piece has been preserved in the museum at Longines, bearing the original serial number 5’810’014. The manually wound mechanical movement, calibre 37.9, features a central seconds hand and a chronograph, with a turnable bezel which made calculating geographical positions more straight-froward. The name Sideograph derives from ‘sidereal’ or star time, and was developed for astro-navigation. "

If that makes sense. (From "A collected man")

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According to "Air Navigation" by P.V.H. Weems, from whence these watches derive their name, civil and sidereal time are normally kept on two separate watches:



My guess would be that the Longines Sideograph wristwatch was never put into production because it's too fiddly to perform the calculations using a single, small watch (whilst flying a plane at the same time!) plus the fact that, should that one watch fail, you'd be in a heap of trouble so, for safety's sake, you'd need to carry more than one watch anyway rendering the single watch solution unnecessary.

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I scanned the above excerpts from my own copy of Weems' "Air Navigation" book but I've just discovered that the entire work is available from the Internet Archive here: https://archive.org/details/airnavigation00weem

So, for anyone that's maybe never used a map or compass and is interested in learning how "old school" navigation works (and for when technology fails and GPS goes pop along with it :biggrin:) enjoy!

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