Dating from 1484, the large dial of the Exeter Astronomical Clock is a working model of the solar system as it was then understood. The sun and moon circle around the earth at the centre of the dial.
The outermost black disc, decorated with fleur-de-lys, represents the sun. It goes round the dial once every 24 hours, pointing outwards to the time of day. The tail of the fleur-de-lys points to the day in the lunar month on the inner ring. The ball inside the lunar month ring represents the moon with half its surface black and half silver. It rotates on its axis to show the correct phase of the moon.
The fixed golden ball in the centre of the dial represents the earth.
A small bell located behind the clock dial chimes the quarters. On the hour, this is followed by the deep sound of the striking of the huge Peter Bell which hangs high up in the tower above.
The text PEREUNT ET IMPUTANTUR below the main dial translates as ‘The hours pass and are reckoned to our account’.
In the 18th century the small upper dial was added with a single hand to indicate the minutes.