The following table shows the preferred rotator angles when the day crew needs to swap optical components or perform dewar fills:
| Angle | Description |
|---|---|
| -90 | Slitmask installation position |
| 175 | Filter installation position |
| -160 | Grating installation position |
| -25 | Fill position, right side (Main fill & standard position) |
| 180 | Fill position, left side and autofill |