NORTHERN COMPUTUS CLOCK
“Northern Computus Clock” Dedicated to the Northern Capital
The original bas-reliefs of the pediments of the north portico (“The Resurrection of Christ”), and the south portico (“Adoration of the Magi”), are reproduced on the pediments of the front and back of the case using the Florentine mosaic technique, the same technique being used in the side panels, on which the stained-glass image of the risen Christ and the mosaic image of the Archangel Michael, from the main altar of St. Isaac’s Cathedral, are reproduced.
Reproduced in miniature, the colonnade of St. Isaac’s Cathedral, framing the dome of the “Northern Computus Clock”, by chance has exactly 24 columns, which is why Konstantin Chaykin chose it as the basis for the circular indications of the world and all-Russia times, the latter displaying the time in each of Russia’s eleven time zones.
The main dial of the clock features a scale indicating the date of the Orthodox Easter in the current year. At the same time, it is possible to calculate the Easter date according to both the old- and new-style calendars. The switching of the display to the new date occurs once a year, namely on the night of 31st December to 1st January. On the back of the movement there is a planisphere with a map of the night sky as seen from St. Petersburg, as well as indications for the season, sidereal time, and the equation of time , the latter being used to indicate the difference between true solar time and average solar time which arises due to the Earth’s elliptical orbit and the inclination of its rotational axis of 23 degrees.
The complications of the Northern Computus Clock
- Computus—mechanical indication of Orthodox Easter date according to the Gregorian and Julian calendars.
- Perpetual calendar with automatic adjustment according to the months’ durations and the leap year cycle.
- Date indicator.
- Day of the week indicator.
- Month indicator.
- Four-digit year indicator (up to year 9999).
- Leap year cycle indicator.
- Moon phase and age of Moon indicator.
- Equation of time indicator.
- Planisphere with the St. Petersburg starry sky map.
- Sidereal time indicator.
- Seasons indicator.
- One-minute tourbillon.
- 24-hour world time indication with local time indication in 11 Russian time zones.
- Power reserve indicator.
- Mechanism of computus module direct drive from a ratchet wheel.
|Housing:||Unique copy 600 × 340 × 242 mm|
|Decor materials and techniques:||Brass, silver, steel, duralumin, mineral glass, gold, marble, flint, rhodonite, violane, xonotlite, lazurite, charoite, guilloche, hot enamel on the guilloche-decorated parts, Florentine mosaic. Diamond-encrusted gold hands.|
|Dials:||Two dials; Nickel-plated or gold-plated brass, decoration techniques: circular and longitudinal grinding, relief decor "guilloche" of four types, gilded decorative overlay details and hour scale markers, all-gold hands inlaid with diamonds, hands made of blued steel.|
|Caliber:||TCO. 03-0 with key wound, 150 × 141 × 82 mm|
|Number of parts:||1375|
|Number of stones:||16|
|Number of ball bearings:||68|
|Semi-oscillations per hour:||18 000|
|Power reserve:||10 days|
The “Northern Computus Clock” is not only the highest achievement of the Konstantin Chaykin manufactory, but of the entire Russian clockmaking industry.
The “Northern Computus Clock”, Konstantin Chaykin’s third clock, was based on the devices for indicating the date of Orthodox Easter which he himself invented. Easter is a church holiday, the date of which changes every year. For that reason, such holidays are known as moveable feasts. For someone not deeply connected with such themes, the changing date of Easter, which happens every year, seems mysterious and unpredictable, as the calculation of this date requires special knowledge and the taking into account of many rules and restrictions.
The Metonic cycle, the solar cycle, indiction, Julian and Gregorian epacts, Julian and Gregorian dominical letters, great indiction , the date of the Paschal full moon…these are the basic concepts used to calculate the date of Easter. Konstantin Chaykin first made an in-depth study of the extremely complex algorithm for the calculation of the Easter date, then created his own calculation method, patented it and used it as the basis for his supercomplicated and completely mechanical device for automatically indicating the date of Easter – it alone consists of more than 300 parts.