  The sunlight reflected from the Moon during a total lunar eclipse has been
transmitted through the Earth's atmosphere on the way to the Moon. The
combination of multiple scattering and inhomogeneous atmospheric
characteristics during that transmission can potentially polarize that light. A
similar (although much smaller) effect should also be observable from the
atmosphere of a transiting exoplanet. We present the results of polarization
observations during the first 15 minutes of totality of the lunar eclipse of
2022 May 16. We find degrees of polarization of 2.1 +/- 0.4 per cent in B, 1.2
+/- 0.3 per cent in V, 0.5 +/- 0.2 per cent in R and 0.2 +/- 0.2 per cent in I.
Our polarization values lie in the middle of the range of those reported for
previous eclipses, providing further evidence that the induced polarization can
change from event to event. We found no significant polarization difference
(<0.02 per cent) between a region of dark Mare and nearby bright uplands or
between the lunar limb and regions closer to the disk centre due to the
different angle of incidence. This further strengthens the interpretation of
the polarization's origin being due to scattering in the Earth's atmosphere
rather than by the lunar regolith.
