The present construction is not a replica. It was inspired by an armillary sphere, possibly built by Eberhard Baldewein around 1570, with a sun-moon mechanism. (Cf. Ludolf von Mackensen: Die erste Sternwarte Europas mit ihren Instrumenten und Uhren. 400 Jahre Jost Bürgi in Kassel, Munich 1979, p. 92 f.)
The replica reproduces the movement of the two stars in fast motion, as it were: One revolution of the celestial sphere does not correspond to one day, but to seven days. One revolution of the moon or month requires four revolutions, one revolution of the sun or one year 52 revolutions. This should simplify demonstrations.
The armillary sphere consists of a base frame that carries the horizon ring with a 360° division. In it is the meridian ring (setting the geogr. latitude), which in turn carries the celestial axis with the resting earth (Terra) in the centre. The instrument is based on the Ptolemaic conception of the world.
The rotating celestial sphere consists of the columellar arcs, the equatorial ring (with 2 x 12 hours, attached to the meridian ring), tropical and polar circles and the tilted ecliptic with zodiac and calendar circle. The two symbols for the sun and moon move over this calendar circle. The age of the moon (29.5 days) and the half or full moon can also be read.
The complete description of the instrument as PDF for download
