In order to achieve the very high resolution needed to observe distant astronomical objects, mirrors of large astronomy telescopes must maintain their shape in all circumstances, despite continuously changing orientations and temperatures. To achieve that goal, mirrors are usually very thick making them expensive, heavy and leading to very strong/stiff mechanical structures to support them. Nowadays, telescope manufacturers favor thinner/lightweight mirrors that are equipped with a network of mirror shaping actuators to compensate for their insufficient stiffness, to constantly maintain the reflecting surface of the mirror in as perfect a condition as possible.