[tz] Prague Astronomical Clock simulation

Kerry Shetline kerry at shetline.com
Thu Apr 21 19:53:44 UTC 2022

While not precisely a timezone topic, I thought a simulation of the Prague Astronomical Clock might be of interest to the readers of this mailing list. I stumbled into this topic a few months ago and I find it fascinating. There aren't too many pieces of machinery that are over 600 years old and still running. Now, of course, it's not still all the original equipment in place today, and there has been a lot of downtime over the centuries as interest waxed and waned over keeping the clock running. Major components of the original clock, however, are still in service today.

Having looked at other old astronomical clocks, the one in Prague, in my opinion, beats them all. For something first operational in 1410, it's a very ambitious and clever design that puts a lot of information into view all at once, in an attractive and compelling way: two different ways of counting the hours of the day, phases of the moon, position of the moon and the sun in the sky, sun rise and set times, and sidereal time.

One of the things I discovered was Jan Tošovský's simulation of clock, which had some attractive SVG graphics, but a user interface that's a bit out of date and clunky by modern UI standards. I used his graphics as a starting point for my own simulation, which can now be found at https://orloj.org/orloj/.

I received a lot of help and advice from Petr Král, the current "clock master", and founder of the Czech Horological Society, about the real, physical clock, its operation and history -- not to mention that he helped make sure my translation to Czech wasn't too far out of whack.

By the way, if anyone takes a look at the site who speaks Spanish, French, or German, I'd love to hear about any suggestions for improved translations you might have. I used to do a lot of work in the past to make sure code was internationalizable, but this is my first multi-language Angular web application.
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