Thank you very much Yokozawa-san for the measurement!

Attached are updated plots with my code.
- Xarm ring down fitting results since May 16
- Yarm ring down fitting results since May 16
- Yarm finesse depencence on ETMY temperature

The measured finesse this morning was:
Xarm 1451(1) with ITMX 73 K ETMX 120 K
Yarm 1312(5) with ITMY 65 K ETMY 75 K

The finesse looks a bit too high considering ITMX transmission is 0.44% and ITMY transmission is 0.48% (JGW-T1809173).
If we believe these ITMY transmission, the maximum finesse without any other losses would be 1428 for Xarm and 1310 for Yarm.
There might be some systematics on the finesse measurement.

By the way, I checked the past data and I guess todays Xarm ring down measurements are done on the GPS times
1242771657 (bad), 1242771991,1242772291
instead of
1242775383, 1242775985, 1242776156
as reported on klog #8974.

The ring down done at 1242771657 had some bump during the ring down and the fitting was not reliable.