With the West Cavity aligned in order to see flashes on the B8 temporary photodiode (SWEB_B8_PDTemp_DC) I selected a period of time when the cavity was fast enough to observe a clean ringing on the transmission peaks but slow enough so the carrier peaks could be differenciated from the HOMs. So I took a period of 400 seconds (starting from GPS:1155463600) and I selected all the peaks corresponding to the 00 mode (I put a threshold on the power at 4 V). After I fitted the transmission peaks taking in account the ringing in order to obtain the speed of the cavity and the Finesse, as done in entry 33795. Figure 1 shows one of the fits.

I selected the fits where the velocity of the cavity was higher than 0.85 um/s because the critical velocity of the cavity is 0.4 um/s which means that the ringing does not appear under this value and the fits are better if the ringing is important (meaning at higher velocity of the cavity). With this criteria we plotted an histogram of the finesse obtained from the fit of the remaining peaks (49 good fits). Figure 2 shows this histogram, which gives us an average finesse of 462 +/- 7. It is compatible with the theoretical one (455), but notice that the analysis was made for an unkown alignment state so a further careful study should be done later on.