A rare and important Sun-Star Chronometer by Ulysse Nardin for the Batori Computer Co. No. 001

A rare and important Sun-Star Chronometer by Ulysse Nardin for the Batori Computer Co. No. 001:

Ulysse Nardin, LeLocle, for the Batori Computer Co. Inc., New York, a rare and important “Sun – Star Chronometer” aviator’s navigational watch with outer, protective case, 30 jewels, stem wind and pin set, adjusted to five positions, cotes de Geneve decorated, rhodium plated, two train movement with differential, controlled by a single lever escapement with compensating alloy balance and micrometric regulator in a brass, snap back and bezel, open face case with black finish, the bands with crowns and pushers for adjusting the seconds and hour angle displays, black 24 hour dial with spade and poker hands, constant seconds at 6:00, sidereal hour angle arc degrees and minutes displayed at 3:00 and 9:00 respectively, the central red hand indicating arc seconds at the periphery, serial #124505 (movement), #001(Batori Computer Co. number), 70mm, together with it’s original cylindrical, velvet lined protective container with identification plaque, case, dial and movement signed

Condition

CASE: Minor losses to black finish on case band, pendant, and bow; A few spots of corrosion on pendant with corresponding loss of finish; Inside of case back with minor fingerprint staining; Cuvette edge and adjacent surface with localized, minor marks and scratches from case knife. DIAL: Very good. HANDS: Very good. MOVEMENT PLATES: Very good; Appears never to have been disassembled. MOVEMENT FUNCTION: Gummy, dirty; Will run briefly; Needs service. Outer case very good, with minor marks and fine scratches; Top with small gouge above plaque. Developed as a navigational tool for aviators, the Sun-Star chronometer was intended to make navigational computation faster and simpler than the methods using air almanacs or slide rules. Invented by Oscar Batori and Raymond Nardin, the watch contains two separate trains, controlled by a single escapement. A planetary differential allows for the two trains to indicate solar time and sidereal hour angle, the sidereal being represented in arc degrees, minutes and seconds. The chronometer was tested at the Greenwich Observatory and passed tests for accuracy, although it seems not to have caught on among aviators. In vol. 17, No.1 of the Journal of Navigation, Air Marshal Sir Edward Chilton stated that “Current astro techniques using the periscopic sextant require altitude and azimuth to be precomputed in order to set these values initially on the sextant. When the chronometer was used to assist in precomputation, increments of G.H.A. had to be applied to the chronometer reading in order to obtain the G.H.A. of Aries for the time of the astro shot. Used in this way, the chronometer offered little advantage over the air almanac.” A Ministry of Aviation test at Boscombe Down stated that “The chronometer was found useful when sighting celestial bodies on an opportunity basis, when up to 20 seconds of time was saved in obtaining L.H.A.; a process which takes about 30 seconds using the air almanac”. In addition to this relatively lukewarm reception, others were also working on timekeepers that would simultaneously display solar and sidereal time, including a solar – sidereal synchronous motor for driving quartz clocks, developed in the Soviet Union by Smirnov, Stepanov and Tovchigrechko. As a result of these and possibly other factors, the Sun – Star chronometer was not a success, and very few were produced. The highest serial number known to us is 004, sold at Sothebys Geneva, Nov. 12, 2020, lot 616. That example appears to have been altered, the case now gold plated, and with a glazed cuvette. It also lacks the outer case. Provenance: Oscar E. Batori, to his son Louis E. Batori, thence to the consignor, circa 1960, Dimensions: 2.25in x 4.5in x