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 15 degrees | Circular, concentric | The entire outer circle on the back of an astrolabe. |
| Zodiacal signs | 0 - 30, Zodiacal divisions, equal or unequal | Every 10 | Circular, concentric | Circular scale immediately inside the outer scale - refers to the full circle |
| Calendar | First day of the month - Last day of the month, Days of year | Every 10 days | Circular, eccentric | Circular scale second in from the outer scale - refers to the full circle. |
| Unequal hours | 1 - 12, 1/12 of daylight | Not numbered hours | Arc | The upper two quadrants of the back of the instrument |
| Shadow square | 1 - 12, Fingers | Not numbered fingers | Box | The lower two quadrants of the back of the instrument |