Love the wide field 6188. Yes unfortunately that looks like ice. You could try a warmer temperature in the meantime but yes a CCD chamber purge and regas looks needed. There probably is a temperature where the ice doesn't form. Perhaps -5 but for sure 2C.
Looks a lot like this image! (except this is a tad oversharpened on the ridge):
http://www.pbase.com/gregbradley/image/150480976/large
Greg.