Lot 15

Strömgren og Olsen, Cornelius Knudsen, Kobenhavn No. 568, Case No. 52760, Cal. 19''', 60 mm, 177 g, circa 1910
A very rare navigator deck watch, so-called "combined sidereal and mean time watch". Developed for astronomical navigation at sea
Case: silver, polished. Dial: enamel, subsidiary dial with radial Arabic 24 hours at "3", subsidiary dial with radial Roman hours at "9", outer radial Arabic minutes, subsidiary dial for auxiliary seconds, continuous 24h sidereal time as well as a chosen time zone or Greenwich time, signed, two spade hands, single Breguet hand and a single hand with sun pointer. Movm.: precision bridge movement, frosted, gilt, wolfteeth winding wheels, screw compensation balance, index spring fine adjusting device.
Sidereal time is the time it takes the earth to make one full revolution around its axis. Since it is based on the Earth’s rotation relative to the fixed stars, it is called sidereal or star time (sider = star in Latin). The sidereal day has 23 hours, 56 minutes, and 41 seconds.
Bibliography: Jendritzky, Hans and Dittrich, Herbert, "Eine Sternzeituhr 'Patent Strömgren og Olsen'", Klassik Uhren, January 1995, p. 56, and February 1995, p. 72.
Svante Elis Strömgren, Jens Olsen, and Cornelius Knudsen
These talented Danish watchmakers were the first to obtain Danish patent No. 22822 of February 11, 1918, for their invention.

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