8  The Instrument Rotator

8.1) Introduction

8.2) Moving the Rotator

8.1. Introduction

The telescope is equipped with an instrument rotator. The entire suite of instruments, including the MIS, are attached to the instrument rotator. The field orientation of the finder and guider cameras is therefore affected by the position angle of the instrument rotator.

8.2. Moving the Rotator

The instrument rotator can only be moved manually from inside the dome. The position angle of the rotator is displayed to the nearest 0.25 degree on a mechanical decker mounted to the mirror cell under the polar axle. Note that there is a 4^o offset; when the decker reads 4^o the rotator is actually at 0^o.

To operate the instrument rotator:

• Unclamp the table lock (large starred knob) using you left hand.

• Turn the table using the knob near the decker using your right hand.

• Re-clamp the table while holding the rotation knob to prevent creep.

Be careful to watch the power cables from the mirror cell to the rotator table. The main instrument cable loop may also become taunt, especially when working in the far north or south. The rotator can be moved by +/- 90^o from its home position.

The autoguider rotator angle must be reset for each position angle of the instrument rotator through the autoguider window.