Calibration of the EKPol K-corona imaging polarimeter

The Dual Rotating Retarder Polarimeter technique has been used for the calibration of the EKPol polarimeter, which is a K-corona imaging instrument based on a Liquid Crystal Variable Retarder (LCVR), and designed to measure the linear polarized radiation coming from the solar corona during total solar eclipses. We put a major emphasis on the EKPol properties at different wavelengths and temperature. In particular, the chromatic dependence of the LCVR rotation prevents from using large band observations, owing to the loss of contrast in the measured modulation curves. This study is also intended as a basis for the design of achromatic LCVRs.