see bstiltqpdcal20190316.png for the calibration curve for the BS tilt QPD.
The calibration factors are 0.004063 mm/counts for horizontal and 0.004534 mm/counts for vertical.
Using the length parameters from 8417 and assuming an incident angle of 36.9 º (same as the SRs), the "linear" range for pitch is ±177.6 µrad and ±200.1 µrad for yaw.
For now, the OL2EUL matrix is
| TILT_PIT | TILT_YAW | LEN_PIT | LEN_YAW | |
| L | 0 | 0 | 0 | 0 |
| P | 1.76971116 | 0 | 0 | 0 |
| Y | 0 | 1.98311972 | 0 | 0 |
