Abe, Marc

First we realigned the setup and tuned both HWP and QWP to inject s polarization.

With ceiling lights off we got :

hwp = 5.5 deg seems pure s
s = 915mV
p = 9.98 mV
hwp = 320.5 deg
s = 22.2 mV 
p = 805 mV

We installed the Soleil-Babinet compensator and tried to align it with auto-collimation.

However, while acting on the yaw steering screw, the retaining spring jumped outside the mount (even if we didn't felt any resistance or didn't reach the end of the screw range...)

Matteo helped us to reinstall it using the ones of an old mirror mount.

Once it was fixed, we could align the SBC without issue.

Tuning the SBC to reach maximal s polarization at the readout we measured :

s = 20.4 mV
p = 652 mV

We can not reach as pure s polarization as before ...

Next step is to use the detent stop by 45 deg and use the Vernier screw to reach again pure s polarization, press the zero of this Vernier, move it again so to reach the next s polarization.

We measured d  = 13.365 mm and got :

s = 21 mV
p = 673 mV

d is our calibration parameters and we can now use it to start measurements.