Methodology: we take a 30 minute dark dome exposure with a standardized setup (g1 s2.0 GG385) to assess the presence of residual light in the dome environment.

A test case is shown above. The background scattered light was about 3 e/hr. There were three traces of scattered light. A small green LED trace seen at lower left, which was found to be due to the SAMS mirror controllers under the primary. The mirror controller LEDs have since been taped over. A faint 9000A IR LED trace in the center right was found to be caused by the fiber optic communications connected to the moving baffle viewing camera, now discontinued. The origin of the red LED trace near the middle has yet to be identified.