This section describes how to set up the apodizing phase plate mode.

Set the rotator

• use +90 or -90. Don't use 0/180 because LN2 spills out at 180.
• Ask the AO Operator to make WFS track rotator angle. Otherwise, the WFS and DM will be rotated relative to one another.

Align the phase plate

• Switch Clio to image the pupil plane for alignment.
• The camera lens must be moved in and out manually. On the Clio cryostat, turn the camera lens knob CCW to position 1 (you will feel a detent). Position 2 is the camera lens (focal plane).
• Move in the phase plate (in Clio Motor Control)
• Power on (checkbox) - this is slow to respond........Be patient
• Advanced options (checkbox)
• Move pupil stop 1(2) positions CW to M'(L') phase plate
• At the science wavelength (or nearby narrow band) take and image to check the alignment. See images below.
• Use fine adjustment to move central obscuration to correct position (start with jumps of 100). There is significant backlash.

Move the camera lens back into position for observing

• Switch back to detent 2 on the brass camera lens knob
• Follow a similar procedure to realign the pupil stop. For images see the Beginning of the Run section.

APP placement (left to right): too low, correct, too high. The key point to notice is the small dot at the center of the phase plate, which masks a bright spot. When the plate is aligned, the bright spot is completely blocked.