Example of a path of the UVES slit across the reconstructed Moon image during the 600 s exposure in the umbra. The slit, 10 arcsec long and perpendicular to the path, remains at ≈936 arcsec from the umbra edge, while the slit path over the Moon was ≈330 arcsec long (length of the yellow line). The mean reflectivity is measured along the path, taking into account a 10 arcsec pointing error in both RA and Dec directions. The terrain reflectivity fluctuates by σ = 13% along the path in this bright lunar region, and the error on the mean reflectivity due to pointing uncertainty is estimated to be about σ = 4%.