Adaptive Optics for Extremely Large Telescopes 4 – Conference Proceedings

The European Solar Telescope is a 4-m planned facility designed to have high spatial resolution capabilities tounderstand the mechanisms of magnetic coupling in the chromosphere and the photosphere. It will feature both aconventional and a multi-conjugate adaptive optics (AO) of similar complexity than the systems for night-timeExtremely Large Telescopes. A particularity of solar AO is that it uses the solar granulation as a reference; therefore thewavefront sensing is performed using correlations on images with a field of view of ~10”. A sensor collecting such awide field of view averages wavefront information from different sky directions, affecting the sensing of high altitudeturbulence, the sampling of which does not depend anymore on the size of the subapertures only, but rather on the size ofthe projection of the extended field of view. Understanding this effect is crucial for the design of future solar facilities,i.e. to choose the adequate height of the DMs on MCAO systems, and also to predict the quality of the reconstructionthat such system would be able to achieve. For that reason, we have studied wide field sensing and found the analyticalequations that describe the process, in order to use this information as an input to improved designs of solar AO systems.