<title>ESO VLT: III. The support system of the primary mirrors</title>

Active optics in modern large optical telescopes

“…To reach the CIR specification, which is equivalent to σ t ≈ 0.02 arcsec, the primary mirror would have required approximately 400 supports, which would have added significant complexity and cost. Instead, the specification could be reached by replacing each of the single point supports by tripods (Schneermann, Cui, Enard, Noethe and Postema [1990]). According to sects.…”

“…Since a basic passive support was required for a pure closed loop operation, a hydraulic support system with all supports connected in each of the three sectors was chosen as the passive part of the axial support system. To avoid pressure differences due to gravity in inclined positions, it was designed as a two chamber system (Schneermann, Cui, Enard, Noethe and Postema [1990]). The active part has electromechanical actuators which work in series with the passive support and therefore add the correction forces to the passive ones.…”

Analysis for the stick-slip motion of differential power screw actuator

“…Nowadays many telescope active optics systems have been equipped with such actuators, for example, NTT, VLT, SUBARU, LAMOST and so on [1][2][3][4] .…”