A limited number of observations were performed in a test mode referred
to as `coronographic' mode. In the coronographic mode the
3
lens was used in combination with the small Fabry mirror on the CAM
entrance
wheel (Section 2.2.1). In this configuration the field
stop (the Fabry
mirror) projected a field image smaller than the detector array, so
that the outer parts of the detector array were unilluminated by the
sky. Light from a source positioned so that its image fell just off
the edge of the Fabry mirror was discarded, so that the
configuration worked similarly to a coronograph.
The object to be blocked was moved just outside
the edge of the field stop to map the surrounding emission.
There were only a few observations done this way and they need interactive
analysis to be studied.