Corrects distortions in the shape of large, thin primary mirrors due to gravitational and structural flexing to provide a smoother surface. Typically operates at a few hertz and uses actuators to align the mirror.
The techniques by which corrections are made to the shape of a large mirror or radio dish to adjust for minute distortions in its shape. These variations arise as a telescope is subjected to forces such as gravity and temperature changes.
Collection of techniques now being used to increase the resolution of ground-based telescopes. Minute modifications are made to the overall configuration of an instrument as its temperature and orientation change, to maintain the best possible focus at all times.
Optical elements whose position or shape is continuously controlled by computers
a method that allows the correction, on an astronomical image, of the defects due to the deformation of the mirror of the telescope. It is carried out during the acquisition phase, by the actuators, which are "pistons" situated under the mirror, that constantly correct the deformations due to the movements of the telescope or to sudden changes of temperature.
Active optics is a relatively new technology for reflecting telescopes developed in the 1980s, which has more recently enabled the construction of a generation of telescopes with 8 metre primary mirrors. Active optics works by "actively" adjusting the telescope's mirrors. This method is used by, among others, the Nordic Optical Telescope, the New Technology Telescope and the Keck telescopes, as well as all large telescopes built in the last decade.