There are two polarimetric modes for Omega-Cass: For very compact or point like objects the double-imaging or Wollaston-mode is
used: Two Wollaston prisms are providing double images of about 17 arcsec beam separation (f/10), one in North-South direction, a second
one for a position angle of 45 deg. Wollaston prisms are perfect polarizers in the 1-2.5 Ám region. The beam separation depends of the
wavelength. A calibration curve is available

    The second mode uses wire-grid polarizers which provide single linear polarized images. Four single images have to be taken through the
four offered analyzers which are mounted at position angles of 0, 45, 90 and 135 deg.