Rule, Regula, Pointer and Alidade Images
Alidade Image:
| Date | ca. 1650 |
| Maker | Muḥammad Mahdī |
| Place | Persia |
| Material | Gilt brass |
| Inventory no. | 50143 |
| Acquisition | Presented by Lewis Evans in 1924 |
Alidade
| Appearance | Tip | Sights | Pinholes | Notches | Description |
|---|---|---|---|---|---|
| Double-ended, original. | Simple | Rigid | Double | None |
Scales
| Type | Range & Units | Numbered | Geometry | Location |
|---|---|---|---|---|
| Sine/Cosine | 1 - 60 1/60 of quadrant radius | Every 5 | Linear | Rule, right arm |
| Unequal hours | 1 - 12 1/12 of daylight | Every 1 hours | Linear | Rule, right arm |