Astrological aspects of the planets
This instrument is clear evidence of the links between the astrolabe and astrology. On one side (the smaller image below) is an astrolabe for a single latitude (33 degrees), and on the other an astrological volvelle, used to find the positions of planets and other celestial bodies, especially in relation to the traditional astrological houses. The scales comprise abbreviated names of the heavenly houses, a solar calendar, the zodiac, its decanates and their rulers, and symbols of the elements (fire, air, water and earth) attributed to the several signs and quarters of the zodiac. The lowest movable disc carries eight pointers which were used to determine the principal astrological aspects. The eight upper pointers which are attached to individual movable discs served to mark the position of the seven planets and of the nodes of the moon.
Astrolabe and Astrological Volvelle, Italian, later 15th century (Inv. 45127)