The back contains 5 scales of the following types:
Type (click to view scale details) |
Range & Units | Numbered | Geometry | Location |
---|---|---|---|---|
Degree | 0 - 90, Degrees | Every 5 degrees | Circular, concentric | The entire outer circle on the back of an astrolabe. |
Zodiacal signs | 0 - 30, Zodiacal divisions, equal or unequal | Every 5 | Circular, concentric | Circular scale immediately inside the outer scale - refers to the full circle |
Calendar | First day of month - Last day of month, Days of year | Every 5 and end of the month days | Circular, eccentric | Circular scale second in from the outer scale - refers to the full circle. |
Unequal hours | 1 - 6, 1/12 of daylight | Every 1 hours | Arc | The upper two quadrants of the back of the instrument |
Shadow square | 1 - 12, Fingers | Every 4 fingers | Box | The lower two quadrants of the back of the instrument |