Prague City Line » The Old Town Astronomical Clock

The Old Town Astronomical Clock – what is hidden inside

The Old Town Astronomical Clock works with help of many toothed wheels and little wheels that make the individual devices and appliances move. These parts together create the technical centre of the clock on which its function depends completely. Let´s learn more about this sophisticated system now.–

Old Town Square

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How the device operates
After the Astronomical Clock had been constructed it was driven only by one single machine. In the 16th century it drove both the astronomical dial and

the calendar board. As the time passed by it was modernized and its mechanics were improved. So the astronomical clock is currently composed of several smaller appliances and gadgets which together form an integral unit. Each of them holds a particular function and dominates a relevant part oft the astronomical clock. The Old Town astronomical Clock is composed of: the main device, the machine of the 24-hour-dial, the stroke machine, the months, the machine for the motion of the apostles, the calendary machine and also Božek´s chronometer. The individual devices are interconnected although their functions are completely individual and independent.

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Look into the heart of the astronomical clock
The most important part of the whole mechanical part is the main machine to which other appliances are connected. Originally it used to be together with the indicing device driven by a 80-kilo-weight. However, the original device was in 1866 replaced by Brožek´s mechanical chronometer. This resulted in improvement (precision) of the astronomical

clock´s functions. The main part of the device is composed of three toothed wheels determined for the motion of the Sun, the Moon and the Zodiac. The wheel of the Sun turns around its axis once in a day. It takes the Sun one year to go round all the Zodiacal signs and based on that it is defined in which Zodiacal sign is the day situated. The 24-hour-dial is an essential component for the operation of the astronomical clock. It is a mechanism which makes the outer wheel of the Old Czech dial turn. There are twenty-four German numbers set at the perimeter to indicate the Old Czech Time where the day starts by the sunset. These numbers were used especially during the rule period of Charles IV. We will discover more about them in another article.

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The mechanism of the astronomical clock
The stroke and bell machines are another important components of the astronomical clock. These appliances ensure through their motion that the Old Town Astronomical Clock strikes the exact time. Therefore numerous ringers conduct from the device which are in the right time used to control the bell but also the cymbalo. With help of the ringers that lead from the shoulder of the stroke levers of the stroke machine, the cymbalo strikes the exact hours. The strokes take place every hour after the doors with the figures of the apostles close. For visualization of the Moon and all his phases the Old Town Astronomical Clock uses the device of the Moon. The Moon is represented by a small ball which contains both the dark and light hemispheres. The phases of the Moon of the astronomical clock are generated by turning of these hemispheres.

Animation of the apostles
Another mechanism we will describe now is used for setting the statues of the apostles into motion. This device starts to work automatically every full hour. The apostles are placed in small wagons and pulled forward with help of the device. The movements of the statues are ensured by a spring so the figures can shake their heads, give blessings with their hands etc. This device also affects the opening of the shutters and motion of the statues such as the Death or the Miser on the outer side of the astronomical clock. Besides the already mentioned figures the device also regulates the motion of the rooster.

How to get to Old Town Square:
Address:
Staroměstská radnice (Old Town Hall)
Staroměstské náměstí 3, 4/1,
Praha 1 – Staré Město, 110 00

GPS: 50°5’13.571″N, 14°25’14.397″E

Connection:
Tram: 17, 18, 53 Staroměstská (then walk along Kaprova street)
Bus: 133 Staroměstská (then walk along Kaprova street)
Metro: A – Staroměstská (then walk along Kaprova street)

Transport connection:
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Information on Prague transport: click here
Information on Prague public transport: click here

Photogallery of Old Town Astronomical Clock (Orloj)