8/16/2019 How to Read Prague’s Astronomical Clock
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Prague’s Astronomical Clock:
The Astronomical Clock (Pražský Orloj) in Prague is one of the
highlights of Old Town Square and one of
the top sights in the entire city. Most tourist think its cool,
take and photo and move on, but the clock is
even cooler if you know how to read it. The clock itself is made
of 3 parts the Astronomical Dial (shown
below), the Walk of the Apostles Figurines, and the Zodiac Dial
on the bottom. There is a lot going on
with the clock which can be overwhelming, but we will try our
best to make it easy.
8/16/2019 How to Read Prague’s Astronomical Clock
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How to read Prague’s Astronomical Clock:
The Astronomical Dial (shown above) is the time telling part of
the clock and was built in 1410. It shows
position of the Sun (10) and Moon (11) in the sky with a
mechanical clock in the center of it.
The first thing to examine is the stationary background of the
Astronomical Dial which pins you the
observer standing in Prague right in the center of an Earthly
map. Surrounding the Earth are colored
rings that represent the current sun light with the bottom dark
circle being night time (7), the orange to
the left being day break (5), the grey to the left being sunrise
(4), the blue on the top being daytime (2),
the grey on the right being sunset, the orange on the right
being twilight, working your way be to night
time. These colored rings for the daylight move throughout the
year as the days grow longer and
shorter.
On the edges the of the Astronomical Dial the ring of Roman
Numerals show the Modern 24 Hour Clock
(1) we are used to today set to Central European Time. Follow
the Golden Hand (9) to see the current
time on the standard 24 hour clock. Outside of the standard
Roman Numerals is another ring with
Schwabacher Numerals showing Ancient Bohemian Time (8) that went
off Italian hours. In Italian hours
they still used a 24 hour day, but the day ended and reset
officially at sunset. Throughout the year the
ring of Schwabacher Numerals rotates to keep the end of the day
lined up with sunset which can be
anywhere from 4-8 pm during the year using modern hours. Easiest
way to think of it is that Sunset is 0
hours and each hour is the time after Sunset.
When using the ancient Czech time it is important to know that
while they changed when the day ended
based on the length of daylight, the day light and night time
hours were always divided up into 12 parts
each regardless. Because the length of the day time changes
throughout the year they used an odd
system called Unequal Hours or Planetary Hours where the length
of the 12 daytime and 12 night time
hours themselves changed in to keep 12 night hours and 12 day
hours. The position of the Gold Sun onthe Golden Hand in relation
to the Golden Arch Lines on the background will tell you what time
it is
based on Unequal Hours. Notice how the Arch Lines on the top of
the clock have the numbers 1-12 on
them going from Sunrise on the left to Sunset on the right? The
Gold Sun moves up and down the
Golden Hand throughout the year to narrower or wider spots in
the Golden Arch Lines showing the
Unequal hours are longer or shorter.
The Moon along the Zodiac Ring (13) spins around the clock
representing its orbit around the Earth and
it also has both a black and white half that rotate to show the
current cycle of the Moon.
The small Golden Star (6) shows the position of the vernal
equinox and measures Sidereal Time based
on its positions in relation to the Roman Numerals on the outer
ring.
The Zodiac Ring move so the sun goes across it counter clockwise
marking the current position in the
Zodiac year.
The relation of all the celestial items are a little weird today
as when the clock was built most people
believe that everything revolved around the Earth on an ecliptic
plane and it wasn’t until the 1500s that
