Which isoplanatic patch size for high angular resolution techniques

The isoplanatic patch size is of interest to reach a high performance with an Adaptive Optics system, since the reference star for its calibration should be located in the same isoplanatic domain than the science source. Different techniques and methods have been developed leading to estimations of the isoplanatic patch but all are model-dependent. We first present a review of these techniques and methods of isoplanatic patch size measurement. We developed a new technique for the estimation of the isoplanatic angle based on an extended object. This technique is now part of our new turbulence profile monitor PML based on the observation of the Moon limb or Sun edge. The first statistics of the isoplanatic angle with this new technique are presented and compared to the exiting techniques based on scintillation measurements or other turbulence parameters such as Fried parameter and/or C 2 n profile.