Famous Astronomical Clocks

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Astronomical Clocks

What is an Astronomical Clock?

An astronomical clock is a clock that shows the time of day as well astrological information. This information could be the location of the sun and moon in the sky, the phases of the moon and its ecliptic condition, sidereal time, the current zodiac sign, and more, depending on the individual clock.

Astronomical clocks are special clocks that we felt deserved some extra attention, in the form of a new post on OnlineClock.net‘s blog.

Astronomical clocks differ from the clocks we normally see because they give us an array of information, instead of just the time of day. I suppose life has gotten too complicated for most of us that the time of day is quite enough to track! It would be unimaginable to hear someone say: “What time do you have, and by the way, what phase is the moon currently in?” Without a doubt, this could garner some strange looks from others. Still, astronomical clocks are quite impressive and have various features that are simply captivating. During the Middle Ages, master clock makers built many mechanical clocks. The astronomical clock was one that amazed the people during that time in history. They believed that it was a magical device. That may explain its popularity during this time period. Today, they are generally historical displays which are considered engineering marvels, aesthetically pleasing and they have precise, fully operational mechanisms for those who enjoy following the planetary positions.

Historical Origins of the Astronomical Clock

In the fall of 1900, a team of sponge divers who were under the command of Captain Dimitros Kondos, were on their way home after a diving expedition when a storm necessitated the crew to take shelter. They anchored near the Greek island of Antikythera. During the wait, they decided to dive for more sponges. One of the divers discovered an ancient shipwreck dating back to the second century B.C. Among many artifacts discovered from the shipwreck was the Antikythera mechanism. This mechanism was used by the early Greeks to calculate the position of the sun, moon, and the stars at any given point by use of complicated metal gears. The exploration of the shipwreck continued for a year and the research continues today on the capabilities of the Antikythera mechanism. This mechanism was the first known example of an astronomical clock, and is considered a marvel of engineering for the time in which it was constructed.

Development of the Astronomical Clock

During the 11th century, the Sung Dynasty of China created the water driven astronomical clock for a clock tower in Kaifeng City. Su Sung incorporated an escapement mechanism and the earliest known endless power chain drive for their clock tower. Contemporary Muslim astronomers, and their engineers, crafted a variety of accurate astronomical clocks for their uses and observations. This included the castle clock by Ibn al-Shatir in the early 14th century.

European development of the astronomical clock started in the 1300s. Initially, the clocks were unreliable. They were as much as 30 minutes off, in most cases. Later the development of astronomical clocks produced more accurate versions of the earlier models. Usually, astronomical clocks were made for demonstration. The clocks educated and informed people who viewed them. They showcased technical skill, and carried a philosophical message of an ordered universe. During the 18th century, there was a renewed interested in astronomical clocks. The people during that time liked the clocks for their accurate astronomical information, due to a renewed in astronomy and how planets influenced people and agriculture.

Astronomical clocks are still constructed today in a variety of themes and styles. It’s all up to the patron as to what they want to keep track of, and how the clock display will fit in with their home decor. Astronomical clocks possess a perfect technology that people love to display and talk about. Some of the coolest astronomical clocks are quite old and have been displayed for generations. Here are some of the most famous astronomical clocks and their locations:


Strasbourg Astronomical Clock

Located at the Strasbourg Cathedral is an astronomical clock built between 1776 and 1856. It was built by Jean Baptiste Schwilgue. Jean employed 30 workers to complete the project. It shows an array of astronomical and calendar functions and is a marvelous display outside of the massive cathedral. Besides its beauty, one of the more interesting things about this clock is that the mechanisms inside of the clock actually predict the date that Easter will fall on each year.


Olomouc, which is the former capital of Moravia in the Czech Republic, has a great exterior astronomical clock located in their Town Square. It is a rare heliocentric astronomical clock. It dates back to 1420, and was remodeled once each century. It was damaged by the retreating Nazi German army during the last days of the war and was remodeled in the 1940s.

Originally, the clock had religious and royal figures which have since been replace with athletes, workers, farmers and scientists. The lower dial represents the sphere of Earth, and indicates minute, hour, day month, year and the phase of the moon. The upper dial displays a representation of the heavenly sphere, and there is a star map. The sun, earth and planets are displayed against a background of the twelve houses of the zodiac. The third level, which is the highest, is where the saints and apostles once paraded during the daily musical display each day at noon. The current display is now performed by worn-looking volleyball players, auto mechanics and factory workers.

There is an intricate background mosaic which covers the clock’s entire height of 14 meters. This background mosaic has a representation of the 12 seasons, and two traditional festivals which are known as the ride of the kings and the processions of maidens.


Lund Cathedral Astronomical Clock

The astronomical clock located at the Lund Cathedral in Sweden was constructed at the end of the 14th century. It was formerly in storage since 1837, and was restored in 1923. When the chimes play, six wooden figures representing the three Wise Men and their servants pass by Mary and Jesus.

The Ramsus Sørnes Clock

Ramsus Sørnes Astronomical Clock

The most complicated astronomical clock ever constructed was made by a Norwegian named Ramsus Sørnes (1893-1967). The clock is characterized by its complexity. Features of this clock include locations of the sun and moon in the zodiac. It has a Julian calendar, Gregorian calendar, sidereal time, GMT, local time with daylight savings time displayed, including leap year. Also present are solar and lunar cycle corrections, eclipses, local sunset and sunrise, the moon phase, tides, sunspot cycles, and a planetarium which includes the 248 year orbit of Pluto. All the wheels are made of brass and are plated in gold. Each dial is silver plated. This clock has been displayed in museums all over the world. This remarkable clock will probably be the last one of its kind to be hand-designed, and made by one man. It is true craftsmanship. The clock was sold in 2002 and its current location is unknown.


Jens Olsen Astronomical Clock

Copenhagen’s city hall has a complete astronomical clock on display. It is set in an interior glass cabinet. The clock took 50 years to design and was designed by an amateur astronomer, and professional clockmaker, Jens Olsen. Some of the components were inspired by the Strasbourg clock, which Olsen studied. It was constructed and assembled from 1948 to 1955. In the mid to late 1990s, the clock was completely restored by the Danish watchmaker, and conservator, Soren Andersen.


The astronomical clock in Prague is probably the most famous of all the astronomical clocks in existence. It is located at the Old Town Hall in Prague, Czech Republic. It is also known as the Prague Orloj. The center portion of the clock was completed in 1410. There are four figures that move in the display every hour, including a skeleton that is representative of death that strikes the time. Each hour, there is a presentation of statues which are representative of the Apostles. The statues are located at the doorway, right above the clock. At noon, all twelve are represented in a display. A calendar display was added to the clock in 1870. The design of the building is Gothic and it presents a very impressive display.

During World War II, the clock was nearly destroyed by a fire set by Nazi German soldiers. The townspeople were heroic in their efforts to save most of the parts. Gradually, the clock was renovated and finally completed in 1948. In 1979, the clock was cleaned and renovated. According to local legend, the city will suffer if the citizens neglect the clock (!).

The clock indicates five kinds of time; the Central European time, the unequal or temporal hours, the Bohemian or Italian hours, the position of the sun in the zodiac, and the sidereal time. It continually provides a complete range of astronomical data. The dial of the clock shows three independent movements: the mean revolutions of the sun, the mean revolutions of the moon, and the position of the stars. The horizon is indicated by the boundaries of the blue and the red colors on the clock. The dark circle at the bottom displays the astronomical night. There are three pointers that rotate around this dial. One is for the sun, one for the moon and the third is for the zodiac.

The astronomical clock in Prague recently celebrated six hundred years in existence. The birthday display was something spectacular. Video mapping was used to overlay the clock. The display went through the history of the clock as well many sublime projections which were synchronized with sound. The display progressed images mostly representing events that happened during the life of the clock. The display culminated through the era in which NASA landed men on the moon. The video of this display is online, and you really have to see it to appreciate what the company did for the people of Prague and the 600th anniversary of their clock. The display took four months to finish, and was witnessed by multitudes of people cheering wildly at the end of what they saw. Many were left in absolute awe after watching the display.

Here at Online Clock, we believe that astronomical clocks are a combination of technology, mechanics, science and art.

These astronomical clocks are admired not only for their impressive stature, but for the fact that they represent the best of all the aforementioned fields. Many people still have a love for the planets, and a belief that the entire universe is a balance in which we somehow fit into. The clocks play a part in reminding us of that balance. There is an artistic aspect to astronomical clocks that we generally do not see with most clocks. When people see an astronomical clock, they are reminded of their advancements. One cannot help but appreciate the men who came before us and created such impressive mechanisms for future societies to utilize and enjoy. These kinds of things remind us that great accomplishments are possible, and that we need to keep going in a forward, progressive direction, just like OnlineClock.net :).

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