For ground-based astronomy, more and more large telescopes are emerging all around the world. Similarly to space
borne telescopes, for which the use of lightened optics has always been a baseline for purpose of mass reduction of
payloads, same kinds of lightened/light mirrors are then now more and more intensively used also for ground-based
instrumentation for astronomy, requiring larger and larger components. Through several examples of typical past
realizations (class 0.5m-1m) for different astronomical projects requiring light or lightened mirrors for different reasons
(optimisation of mass and stiffness, reduction of thermal inertia, increasing of dynamic performance for fast scanning
purpose,....), the presentation will point out issues for lightening design, manufacturing and control of such parts, as well
as brief overview of the corresponding existing "state of the art" for these technologies in SESO.