Multi-conjugate adaptive optics at big bear solar observatory

A multi-conjugate adaptive optics (MCAO) system for solar observations has been set up at the 1.6-meter clear aperture New Solar Telescope (NST) in Big Bear Lake, California. Being a pathfinder to address fundamental design questions in solar MCAO experimentally, the system is purposely flexible. We deploy three deformable mirrors (DMs). One of which is conjugate to the telescope pupil, and the other two to distinct higher altitudes. The pupil DM can be either placed into a pupil image up- or downstream of the high-altitude DMs. The high-altitude DMs can be separately and quickly conjugated to various altitudes between 2 and 8 km. Three Shack-Hartmann wavefront sensor units are available, one for low-order, multi-directional sensing and two highorder on-axis sensing of which one is used at a time. The flexibility of the setup allows us to experimentally study the various sequencings of DMs and WFSs, which are hard to simulate conclusively. We report on the preliminary results and summarize the design and the configuration options of the MCAO system at Big Bear Solar Observatory (BBSO).