The Very Large Telescope Survey Telescope (VST) is equipped with an active optics system in order to correct low-order aberrations. The 2.6 m primary mirror is supported both axially and laterally and is surrounded by several safety devices for earthquake protection. We describe the mirror support system and discuss the results of the qualification test campaign.
This work deals with the application of parallel robots for the correction of defocus and coma optical aberrations in the case study of the VST (VLT Survey Telescope) telescope, to be installed at the ESO observatory of Cerro Paranal (Chile). The parallel robots are used to change position and orientation of the secondary mirror. The secondary mirror positioning capability is a fundamental part in an active optics system, i.e. a closed loop control system for the minimization of the telescope optical aberrations, where the outer optical feedback coming from the wavefront sensor is used to generate references for the inner motion control loop of the secondary mirror positioning robots. Two devices are presented: a 6-6 Stewart platform where both fixed and mobile platforms are regular and similar hexagons whose vertexes belong to the same plane and are on a circle, and a two stages device composed by a XY table plus a tilt platform. The basic theory of active optics corrections is presented. The kinematics of both devices is solved in connection with the active optics application; first test data are presented.
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