The NICI Focal Plane Mask wheel lies outside the dewar, ahead of the pupil masks and the beam splitter.  These masks provide the central obscuration for coronagraphic imaging.  The masks expected to be available in the initial instrument configuration are listed below.  Because the mask wheel is external to the dewar, it is relatively straight-forward to add or change masks and additional positions are available for user-defined masks. 

Created July 15, 2005, B. Rodgers and T. Hayward

Modified 26 October 2007, E. Christensen