lunation. The moon progresses through its various phases, which depend upon the relative positions of the sun, moon and Earth. The moon’s phases (new moon, first quarter, full moon, third quarter and return to new moon) comprise one lunation. One lunation is approximately equal to 29.5 days.
A very rare and costly precious metal. More than 300 kilograms of ore must be mined to yield a single gram of platinum. By comparison: only 100 kilograms of ore must be mined to yield one gram of gold. Platinum melts at a higher temperature (1,773º C) than gold (1,063º C.) or silver (960º C.). It is harder, tougher and heavier than other metals used in jewelry. Special tools and techniques are necessary to work platinum. Most Platinum is used in a very pure alloy (950) which contains 950 parts of platinum per 1,000 parts (i.e. 95% pure platinum). A platinum watch-case weighs about 35% more than a corresponding case made of 18-carat gold.
These play an important role when a watch’s rate is adjusted. Unlike pocket-watches, wristwatches are worn in many different positions Pocket-watches usually remain in a hanging (crown up) or lying (dial up) position. Precision wristwatches are usually adjusted in five different positions: “crown left,” “crown up,” “crown down,” “dial up” and “dial down.” If the watch is to be designated as a “chronometer,” then the precision of its rate must be monitored during a 15-day ordeal at an official testing site (operated by the C.O.S.C.). In each of the five positions, its average daily rate must be between –4 and +6 seconds; its average deviation of rate must not exceed 2 seconds; its greatest daily deviation of rate must not exceed 5 seconds. All watches are tested at temperatures of 20º, 4º and 36º. If it passes the chronometer test, the watch is given a chronometer certificate.
Maximum interval during which a mechanical movement continues to run after its mainspring has been fully wound.
The precious metals gold, platinum and silver are typically used for the cases of wristwatches. Gold is generally used in alloys designated as 333/1,000 (8 carat), 375/1,000 (9 carat), 575/1,000 (14 carat) or 750/1,000 (18 carat). Admixture of other metals (e.g. copper) determines the alloy’s color. Either 21, 23 or even 24 carat gold is used, for example, in rotors. Platinum with a purity of 950/1,000 is particularly prized because of its understated color.
The ticking timepiece numbers among the oldest and most precise mechanical machines. A movement which deviates from the official norm time by 30 seconds per day (one day = 86,400 seconds) performs with an arithmetical error of merely 0.035%. In other words, its precision is 99.965%. Officially certified chronometers achieve far higher levels of precision and may deviate from perfect performance by less than 0.005%.
A component which activates or deactivates a particular function. On watches with hinged covers, it is pressed to open the cover. The stopwatch functions of a chronograph are started, stopped, and returned to zero by means of a push-piece. The chimes on some repeaters are triggered by a Push-piece.
(for time display in a second time zone) A mechanism which enables the user to directly adjust the indicator of the time in a second time zone through increments of one hour by means of a push-piece.
Precision pendulum clock which was formerly used to test smaller timepieces. Distinguishing characteristic: off-center hours subdial.
A hand moves to indicate something (e.g. the hour or the date) along a segment of a circle (calibrated, e.g. from 1 to 12 or from 1 to 31). When the hand reaches the end of the calibrated scale, it rapidly jumps back to its original position and resumes its forward motion. To accomplish this retrograde motion, the hand is linked, either directly or via a lever, to a small spirally shaped and stepped cam. When the hand reaches the end of its scale, one end falls over the step of the cam, thus instantly returning the hand to its starting position.
An oscillating mass which turns freely and without restriction about its own axis in an automatic watch. Depending on the construction of the self-winding mechanism, the mainspring can be tightened by the motion of the rotor in either one or both of the rotor’s directions of rotation. There are central as well off-center rotors; the latter are also known as “microrotors” or “planetary rotors.” Central rotors turn beneath and across the full disk of the movement; off-center rotors are integrated within the plane of the movement.