| Specification of Precision grade: |
| Tolerance of focal length: |
+/-2% |
| Surface accuracy: |
1/8£f |
| Surface quality: |
20-10 |
| Centration: |
3 arc min |
| Diameter tolerance: |
+0/-0.1 |
| Tc tolerance: |
+/-0.2 mm |
| Te tolerance: |
nominal |
| Specification of General grade: |
| Tolerance of focal length: |
+/-2% |
| Surface accuracy: |
1/2£f |
| Surface quality: |
60-40 |
| Centration: |
3 arc min |
| Diameter tolerance: |
+0/-0.2 |
| Tc tolerance: |
+/-0.4 for <50mm Dia; +/-0.6 for >50mm Dia. |
| Te tolerance: |
nominal |
| coating: |
single layer MgF2 or custom |
| clear aperture: |
>90% |