Sheila, TJ, Betsy, Keita, Jeff 

Over the last 9 days we have moved the PR3 yaw slider by 2 urad (from 151.6 to 149.3) to maintain the ALS beatnotes on ISCT1, to allow locking.  Today we had planned to move PR3 back and realign on the table, but when I set PR3 back TJ saw that the beams were clipped arriving on the table, and not reaching the trans PDs well enough to trigger and lock the arms in green.  The beam was clipping on the prism, so fixing this on the table would have meant moving the periscope mirrors.  We decided to first double check that the green camera for the X arm had not drifted.  

Instead of realigning on the table, we decided to check the camera reference.  TJ skipped shuttering ALS as we relocked, let ADS converge at 2W, and Keita and I ran the green offset servo (reminder, green reference instructions are here).  The attached screenshot shows the QPD offsets and camera offsets that we would have gotten.  These are not large changes to the references, so it doesn't seem that the problem is something like a drift of the camera. We reverted these changes to the green references. 

A screenshot of the camera is attached, which does show the beam is not well centered on this camera. 

We are returning to locking now, but since this has been causing locking troubles and seems to be getting worse over time, we will plan to return to re-align the table next time we are relockign during the day.