| Date |
early 18th century |
| Maker |
‘Abd al-A’imma |
| Place |
Iṣfahān |
| Material |
Brass |
| Inventory no. |
40833 |
| Acquisition |
Presented by J. A. Billmeir in
1957 |
Rule, Regula, Pointer and Alidade Images
Alidade Image:
Rule Image:
Rule
| Appearance |
Tip |
Sights |
Pinholes |
Notches |
Description |
| Double-ended, counter-changed,
original. |
Simple |
None |
None |
None |
It is possible that this rule
is a replacement. Islamic astrolabe rarely have a rule or
pointer
on the front of the instrument. Moreover, the silver
knob
at the bottom of the rete
prevents this rule from rotating around the entire
circle. |
Scales
| Range & Units |
Numbered |
Geometry |
Location |
| Declination |
0 - 90 Degrees |
Every 6 degrees |
Linear |
Rule, left arm |
| Equal
hours |
0 - 24 Times of day |
Every 1 hours |
Linear |
Rule, right arm |
Alidade
| Appearance |
Tip |
Sights |
Pinholes |
Notches |
Description |
| Double-ended, original. |
Simple |
Rigid |
Double |
None |
|
Scales
| Range & Units |
Numbered |
Geometry |
Location |
| Sine/Cosine |
0 - 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 |
