Attached is a plot of the power measured at the base of the IO periscope as a function
of the requested angle in the MEDM screen.

    The following angles may be of interest:
minimum power -25 degrees
maximum power  -70 degrees and 20 degrees

    Measurements were performed with the Ophir power meter, using 3 second averages.

    The requested angle was consistent with the scale etched on the rotation stage.
To check that the half waveplate was not slipping within its mount, angular requests
moving the waveplate from one end to the other were made and the power measurements
were consistent with previous measured values.  So there was no experimental evidence
of the waveplate slipping within its mount.




Jason, Peter