The principle of the spherical Astrolabe is as old as the knowledge of the spherical relationships of the celestial sphere and the Earth's sphere. It is the most illustrative instrument with which one can show the daily movement of the celestial vault in relation to the earthly horizon coordinate system with its altitude parallels and azimuthal circles. A half-hollow sphere is rotated above the fixed earth sphere with horizon coordinates and other line systems, reproducing the celestial vault with selected stars and the zodiac.
Such a spherical Astrolabe was and is a great challenge in terms of craftsmanship. The instrument is at the top of our agenda.