“…The generated high spatial frequency aberrations, the so-called print-through, depend clearly on the specific weight and the elasticity module of the mirror material, on the thickness of M1 and the density of supports. But it can also be influenced by the general type of the support system, for example if part of the weight of the mirror is supported by a continuous pressure field at the back surface as realised in the support of the primary mirrors of the Gemini telescopes (Stepp and Huang [1994]). The stiffness of M1, a central parameter for the active optics design, is a function of the diameter of M1, its thickness and its elasticity module.…”