The Story of The Astronomical Clock

50 Years in the mind and 12 years in the making

Denmark's famous astronomical clock is the outcome of one man's brilliant ideas and his persistence. Generations of visitors to Copenhagen City Hall have become acquainted with this unique masterpiece. Without the carefully prepared design, this clock would not have turned out as beautiful as it became: A free-standing monumental astronomical clock in a delicately built mahogany cabinet, whose lightness contributes to its uniqueness.

Who was Jens Olsen?

Jens Olsen was born in Ribe on July 27th 1872. As a child he showed talent as a locksmith and later became an able instrument maker. When he was 25, Jens Olsen went to Strasbourg, the home of one of that period's technical wonders, the astronomic clock with its perpetual calendar which is to be found in the cathedral. He studied it meticulously and on repeated visits noted its complex functions. Jens Olsen settled in Basel where he worked as a journeyman and studied at the university. The idea of building an even more complete astronomical clock began to germinae.
In 1902, after 5 years of travel, Jens Olsen returned to Denmark, where he established himself as a watchmaker. He won a reputation as an inventive craftsman and scientific institutions entrusted him with many different kinds of assignments. In 1906, he was one of the founding fathers of the Danish Astronomical Society. In the meantime, he carried out numerous calculations and made drafts concerning his dream - the complete astronomical clock.
By the time Jens Olsen was 60, he had made all the necessary calculations. Professor Elis Strömgren declared: "Both from an astronomical as well as from a mechanical point of view, Jens Olsen's drafts rests on solid basis and attests to a combination of two different qualifications which only rarely would be united in one person".

The making of the clock

In 1943, the Danish Employers´ Association awarded the project 100.000 DKK, which was later added to by a subscription among Danish craftsmen. The clock had become a national assignment. Jens Olsen and his friend, Graduate Engineer Axel E. Flint, worked hard drafting the many thousand of parts which would eventually become a clock. Three people were employed and the Technological Institute put workshop premises at his disposal. Jens Olsen's employees were fully aware to his brilliance: "When we met an almost insoluble problem, Jens Olsen would come up with a solution which then appeared obvious, simple and the best".
In 1945, when 10 of the 11 of the works were well under way, Jens Olsen fell ill and died on 17th November. The responsibility for completing the clock fell to the young watchmaker, Otto Mortensen. At this stage, the project still needed to construct the perpetual calendar.
A competition to design the clock's exterior  was won by the architect Gunnar Biilmann Petersen whose design was based on an aestethic balance of elegance and functionalism
Several of the works had to be rebuilt to satisfy Biilmann Petersen´s design. It was not until 1948 that this work was accomplished and even then there was still a lot of work yet to be done. Producing the stainless steel frame was a major problem, the perpetual calendar movement, and the engraving of the delicate dials also took several years.
In autumn 1955, all 15.448 individual parts of the clock were at last complete. After 50 years in the mind and 12 in the making, the clock was set in motion at 1500 hours December 15th by King Frederik IX and Jens Olsen's granddaughter Birgit Olsen.


The world clock - what does it show?
(pictures soon to come...)
Left Section
The top dial shows the time equation (1), local time in Copenhagen (2) and actual solar time (3). The time equation means the time difference between local time and actual solar time. Local actual time is the time usually used. Actual solar time expresses the earth's position proportional to the sun. When the hands of actual solar time show 12, the sun is in meridian.
The dial to the left (4) shows the time at any location on earth.
The dial to the right (5) shows the time of sunrise and sunset both according to local time and actual solar time. The dial is equipped with black and white arch-shaped pieces to indicate the lengths of day and night.
The Gregorian calendar shows the year (6), the day of the week, date and month (7). This perpetual movement sets itself once every 24 hours at midnight.

Middle section
Top dial (1), divided in 12 hours, shows local mean time - Central European time, the daily time 15° east of Greenwich in hours, minutes and seconds.
The perpetual calendar consists of 5 dials, indicating: The Sunday letter (3), the epact (4), the sun circle (5), the indiction (6) and the moon circle (7). Furthermore, there is a calendar showing the 12 months of the year, the days and dates of the week, every moon phase as well as the calculated Easter Sunday - all other holidays according to Easter Sunday. The works of the perpetual calendar are automatically set in motion every New Years Eve at midnight, to calculate the calendar for the following year. It runs for the next 2500 years.

Right section
The top dial (1) shows the present star map over Denmark and the slow precession of the motion of the earth's axis over 25.753 years!
The left dial (2) shows the geocentrical orbit with the Earth as its centre. Here you can obtain knowledge of the sun's and moon's eclipses, the distance between the Earth and the Moon - the apse line and the knot line.
The right dial (3) shows our solar system with the planets Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Uranus and Neptune around the Sun.
The bottom dial shows the year (4) and number of days (5) according to the Julian time period which is 7.980 years. Astronomers use the Julian Time period to register astronomical phenomena.