The LRIS trapdoor is the access door to the front of the instrument. It can be either OPEN or CLOSED. In August 2004 the trapdoor mechanism was re-designed to accommodate the Cassegrain ADC requirements: the former swing mechanism was replaced by a sliding hatch. The immediate advantage is that the trapdoor can open and close in much less than the usual 15-20 seconds, and can be set as fast as 1 sec. In this mode, the trapdoor can be used as a poor man's shutter everytime one of the camera shutters is broken.

Trapdoor functionalities:

The front of LRIS and the open trapdoor. Visible on the right is the offset guider assembly.