... Armagh Observatory, College Hill, Armagh BT61 9DG, +44 (0)28 3752 2928 . ... Circular polarization of the bright side of Iapetus versus wavelength, obtained with FORS2 at the ESO VLT during the night 2011-03-28 at a phase angle of 0.77 . ... It can be noted that a change in signal occurs in circular polarization observations that are taken after rotating the instrument by 90 degree with respect to the intial position angle on the sky. ...