Unless otherwise noted all powers measured with the water-cooled 300 W Ophir power meter.  The ISS was
unlocked but still diffracting light, whilst this does distort the beam it should be constant over the
time scale of the measurements taken.

    Using the locking photodiode over a 5 minute observation time:
  locked: -260 mV to -262 mV
  unlocked: -1.001 V to -1.004 V
Calculated visibility using the locking photodiode is thus: (74.0 +/- 0.4)%

    Using the power meter:
  locked: 30.5 W to 30.6 W
  unlocked: 121.6 W to 122.2 W
Calculated visibility using the power meter is (74.9 +/- 0.3)%

    The power transmitted by the pre-modecleaner was 105.7 W to 106.1 W.  Which suggests a pre-modecleaner
cavity transmission of (86.9 +/- 0.2)%.

    The errors listed above are okay to the precision of the measurement and not its accuracy.
Bearing in mind that the accuracy of the power meter is +/- 3%, the visibility measurement and
transmission measurement are on the edge of agreement.

    Taking accuracy into consideration the visibility is then (75 +/- 4)% and the transmission is
(87 +/- 5)%.  The two measurements are in general agreement but are not very accurate nor precise.