Looking at the SR2 peanuts-shaped baffle, I set the new SR3 alignment offset.
SR3 Old: [430.3, 142.6]
SR3 New: [654.3, -38.8]
The original position was not that bad, it was a bit too the left and low.
After this, I scanned SR2 while centering the AS_C QPD using picos.
SR2 Old: [2963.7, 2728.0]
SR2 New: [1339.7, 1575]
The new AS beam position on the camera is to the left and high.
SR3 details:
Peanuts-shaped SR3 baffle was used as a reference.
The IFO beam is supposed to be in the right hole, the angle between SR3-SR2 beam and SR2-SRM is 29 mrad, the distance from the baffle to SR2 is about 460mm (just by eyeballing the drawing), so the beam separation on the baffle is about 17.5mm.
This means that the SR3-SR2 beam should be about 17.5/2 mm to the left from the center of the right baffle hole.
PR3 YAW offset when the beam just hits the right edge of the baffle was -1394.4, while the offset when the beam was on the center line of the right baffle hole was -194.4.
When looked from HAM5, the right baffle hole looks like an ellipse with the major axis vertical, and the minor radius is 67.5mm.
Therefore the PR3 YAW offset should be
SR3 Y = -194.4 + (-194.4+1394.4) * 17.5mm/2 / 67.5mm = -38.8
PR3 P offset when the beam hits the top/bottom edge of the tallest part of the hole was 2350.3/-1041.7, and the average is 654.3.
This also means that the SR3 YAW slider calibration is off.
For YAW, 1200 urad of the slider offset produced about 67.5mm.
2*angle*16m = 67.5mm -> angle = 2.1mrad.
Therefore, in reality, the SR3 slider calibration for Y is 2.1mrad/1.2mrad = 1.76. (But I'd claim that the measurement error is probably as large as 30% or so).
For SR3 PIT, it's good.
The beam moved from the bottom to the top with -3392 urad slider step. The hole height is 114mm.
2*angle*16m=114mm -> angle = 3.6mrad.
The SR3 slider calibration for P is 3600/3392 = 1.06
SR2 details:
Before SR3 bias was set, AS_C was centered using pico.
After SR3 was done, AS_C was centered using SR2 bias. After this, SR2 bias was [1399.7, 1485.0]. This is our "initial position".
Then SR2 bias was scanned first in Y, then in P, and then Y again.
Attached left is the Y scan and the right is the P scan. Blue vertical lines indicate where I started.
As I was sort of suspecting, PIT was more off than YAW, and anyway I settled on [P,Y]=[1339.7, 1575].
One caveat is that the final position corresponds to one data point where I see a jump in the AS_C SUM (look at the green circle that goes to 1.04). This is repeatable, and I think this is where some stray beam or maybe the reflection from the AS_C goes into the AS_C. I don't think this corresponds to smaller loss. This position was chosen as the final position by eyeballing the peak of the green plot excluding that abnormal data point.