I tuned the dither alignment for the x-arm tonight.

YAW:
 - Dithering PZT1 at 410Hz using oscillator 2. Driving ETM using control bank 2.
 - Dithering PZT2 at 470Hz using oscillator 3. Driving TMS using control bank 3.
 - Oscillator 1 and control bank 1 are currently not used.

PIT:
 - Dithering PZT1 at 380Hz using oscillator 2. Currently not driving anything.
 - Dithering PZT2 at 440Hz using oscillator 3. Driving TMS using control bank 3.
 - Dithering ETMX at 1.7Hz using oscillator 1. Driving ETM using control bank 1.


I didn't use the PZT1 pitch dither because there is a DC offset in the demodulated error signal. Note that PZT1 is input pointing position (PZT2 is angle).
I was able to zero the dither offset byputting offsets into the green QPDs:
H1:ALS-X_QPD_A_PIT_OFFSET = -0.464
H1:ALS-X_QPD_B_PIT_OFFSET = -0.084
Those offsets were chosen such that they only lead to a different PZT1 drive, leaving PZT2 untouched.

Attached is a snapshot of all relevant screens.

Still to do:
 - Relieve script or servo (or move integrators to the suspensions).
 - Automatic turn-off of the servo if the arm power drops below a threshold.
 - Actuation node dither for ITM centring. (I would prefer less mode-hopping for this.)