Meridian Sundial in the Clementunum Astronomical Tower, Prague - Sundials on Waymarking.com

When you visit the Clementinum in Prague, take the tour of the Astronomical Tower. Most do this to enjoy the view over the city but there is an interesting if subtle feature in the tower. A small hole in the south facing window at the top of the tower projects a bright spot onto a meridian strip on the floor and north wall of the room. This strip just below the prominent quadrant with a transit telescope is in a long wooden box with protective doors. This meridian is marked for the position of the solar spot at noon at different dates and solar declinations throughout the year. Just above the meridian strip is a taut wire carefully aligned north in the vertical and horizontal axes.

When the solar spot projected onto the meridian strip is bisected by the wire shadow, it is solar noon. Then a flag was waved out of the window to signal to the gunners in the castle across the river. They then fired the noon cannon to mark Prague Noon. This procedure was established in 1842 and continued until 1926 although Prague switched to Central European Time in 1912.

Sundial Type: Other Related Web Site: Not listed

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