To exactly indicate complex motion of planet seen from the earth.

A dial 25 has a planet window 25a of nearly semicircle. A constellation plate 22 is a transparent disk rotating in accordance with the motion of stars. The ring shape planet plate 24 has pictures 24a and 24b of two planets 180 degrees apart. When the planets set in and is not seen in the sky, the pictures 24a and 24b of the planets can not be seen from the planet window 25a and the planet plate 24 does not rotate. From the time of planet 'rise', one of the pictures 24a or 24b of the planet is shown from the planet window 25 by rotating the planet plate 24 with the same speed as the planet plate 22 and the rotation of the planet plate 24 is stopped when the planets set in. The complex motion of planets going back and forth in the constellation seen from the ground as the clay and hour goes on, is shown by the combination of rotation of the planet plate in one direction and stop.