Longines. A very fine and rare stainless steel Siderograph double split seconds chronograph deck watch

SIGNED LONGINES, AERO-N. NO. 6425248, CIRCA 1939

Details

Longines. A very fine and rare stainless steel Siderograph double split seconds chronograph deck watch
Signed Longines, Aero-N. No. 6425248, circa 1939
With Marine Nationale cal. 21.29, nickel-finished jewelled lever movement, the two tone silvered dial with inner black ring calibrated for 360 degrees with black hand doing a complete rotation in 23 hours and 56 minutes, inner red ring calibrated for degrees, outer blue ring calibrated for 300 divisions, up and down indicator, in circular glazed aluminium case suspended from the aluminium frame with five anti-vibration springs, the springs protecting the movement from deregulation by the vibrations of the aircraft's or zeppelin's engine, all screwed into the wooden transportation box with glazed cover, dial and movement signed
94 mm. diam.

Lot Essay

Accompanied by photocopies of Longines Siderographe Ref. 6081 description and operating instructions in French and photocopies of Heinrich Pavel's article "Der Siderograph", Alte Uhren und moderne Zeitmessung 5/86 edition.

The Siderograph is named after the expression "sidereal" or star time and was originally developed for astro-navigation.

The sidereal time watch is an ordinary watch which is speeded up by adjustment of the mechanism in order that it will indicate 24 hours of sidereal time for every 23 hours 56 minutes approximately of solar time. A Siderograph is a combination of a clock and a navigation instrument and keeps a reference time equivalent to the time at 0° Greenwich longitude.

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