The back contains 6 scales of the following types:
| Type (click to view scale details) |
Range & Units | Numbered | Geometry | Location |
|---|---|---|---|---|
| Degree | 0 - 90, Degrees of arc | degrees | Circular, concentric | The entire outer circle on the back of an astrolabe. |
| Zodiacal signs | Zodiacal divisions, equal or unequal | Every 5 | Circular, concentric | Circular scale immediately inside the outer scale - refers to the full circle |
| Calendar | Days of year | Every 5 days | Circular, eccentric | Circular scale third in from the outer scale - refers to the full circle. |
| Shadow square | Fingers | Every 3 fingers | Box | None |
| Dominical letter | 1583 - None | Inner Circular, concentric | Upper left quadrant (inside circular scales) | |
| Epact | 1583 - None | Inner Circular, concentric | Upper right quadrant (inside circular scales) |
| Transcription | Translation | Notes | Type |
|---|---|---|---|
| Philipvs Danfrieus, Siderographus Regius Generalis Lutetiae exarabat, Anno Salutis 1584 | Maker's signature |