Compton polarization measurements during owl shift 06/25 01:30 : (79.2 +/- 0.5) % 02:30 : (80.7 +/- 0.5) % 04:45 : (79.6 +/- 0.55) % 05:50 : (79.2 +/- 0.72) % 07:40 : (80.2 +/- 0.54) %