The sundial is the oldest known device for the measurement of time and the most ancient of scientific instruments. It is based on the fact that the shadow of an object will move from one side of the object to the other as the sun "moves" from east to west during the day.
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Let´s go looking for Sundials
In The Czech Republik are several thousand of sundials.
Since 2006 I have been collecting Sundial´s fotographs.
In year 2008 I had trip to see sundials in Poland and I want to visit Sundials Museum in Jedrzejów where is large collection of sundials.
In muzeum in Opava I found very interesting portable equatorial sundial of the type invented in Augsburg.
Do you want to make sundials?
My first attempt at the garden and on the wall. The best step to start make sundial is try to costruct any.
Orologi Solari - http://digilander.libero.it/orologi.solari/. Description and user manual in Czech are here.
Sonne - http://web.utanet.at/sondereh. Description and user manual in Czech are here.
Sun - http://relogiosdesol.blogspot.com. Description and user manual in Czech are here.
Astronomical society in Hradec Kralove - Sundials working group
In Czech has been sundials friends society formed.
The working group has been working since 2007 and it is covered by Astronomical society in Hradec Králové.
- Catalogueing of sundials in Bohemia, Moravia, Silesia and Slovakia
- Meetings and Excursions
- 30. 9. – 1. 10. 2006 Observatory and Planetarium in Hradec Kralove (lecture and car trip)
- 9. 4. 2007 One-day car trip to view sundials
- 20. – 21. 10. 2007 Observatory Valašské Meziříčí (lecture and car trip)
- 12. 4. 2008 One-day car trip to view sundials
- 4. - 5. 10. 2008 Observatory and Planetarium in Hradec Kralove (lecture and car trip)
- 18. -19. 4. 2009 Car trip from Prostejov to Zlin and lecture at observatory
- 5. 9. 2009 Prague - Two days‘ sundial trip - first day
- 6. 9. 2009 Prague - Two days‘ sundial trip - second day
- 24. 4. 2010 The Sundial Day in Olomouc, Svatý Kopeček, Dolany, Sternberk and Lošov - litle astronomy observatory.
- 25. - 26. 9. 2010 Two days with sundial trip and lecture - Karlovy Vary.
- 17. 4. 2011 Sundial trip - Ceska Lipa.
- Assistance in the preservation of historical sundials
- Publishing in "Povětroň"
Astronomical society in Hradec Kralove: http://www.astrohk.cz/ashk/
Sundials Working group: http://www.astrohk.cz/ashk/slunecni_hodiny/ (Czech only)
Catalog of sundials in Bohemia, Moravia, Silesia and Slovakia: http://astro.mff.cuni.cz/mira/sh/sh.php
Why is a diference between apparent solar time and mean solar time?
- The plane of the Earth´s equator is inclined to the plane of the Earth´s orbit around the Sun (by 23,5).
- Orbit of the Earth around the Sun is an ellipse and not the circle. When the Earth is closer to the Sun, it moves faster, sweeping through a longer path in a given time (The second Kepler's Law).
- The time displayed by a sundial will vary from the mean time during the year, up to 16 minutes ahead (November 3), and up to 14 minutes behind (February 11), only agreeing around April 15, June 13, September 1 and December 25th.
When does the sundials was inveted?
- It is not known exactly when the sundial was invented. Sundials can be found in many ancient civilizations, including the Babylonian, Greek, Egyptian, and Roman ages. Sundials exist in most countries, in various forms, differing in construction according to the knowledge of the age in astronomy and mathematics, and showing clearly at different periods in the history of a race evidence of influence by other civilizations with greater knowledge. Sundials are also abundant in the far East such as China and Japan, but not as much history of these is known to the Western world.
Who and when the portable sundials was invented?
- Probably the first portable timepiece, came into use around 1500 BOE, knows as Egyptian shadow clock. This device divided a sunlit day into 10 parts plus two twilight hours in the morning and evening.