Museo Galileo
Virtual Museum
    • Setting:
      Room II
    • Maker:
      Giovanni Battista Giusti [attr.]
    • Place:
    • Date:
      second half 16th cent.
    • Materials:
    • Dimensions:
      170x170 mm
    • Inventory:
    • Declinatory (Inv. 3822)

Quadrant consisting of a square plate whose corners stand for the four cardinal points. The "south" corner holds a pivoting index that rotates on the degree scale and is fitted with a magnetic compass. To calculate the declination of a wall on which a vertical dial was to be installed, the instrument had to be placed horizontally with one side against the wall. The compass showed the index's direction relative to the magnetic meridian; with the degree scale, one could read the relative declination, east or west. If held vertical, with the index used as a plumb bob, the instrument could also be used to measure the slope of a plane on which an inclined dial was to be installed. The back of the quadrant is blank. The construction characteristics suggest an attribution to Giovanni Battista Giusti.