An Etymological Dictionary of Astronomy and Astrophysics
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A technique for improving the → resolving power of a telescope by controlling the shape of the main mirror at a relatively slow rate. The → image quality is optimized automatically through constant adjustments by in-built corrective → actuators operating at fairly low temporal frequency ~0.05 Hz or less. → adaptive optics.

→ active; → optics.

A technique for improving the → image quality of a telescope against → atmospheric turbulence in which image distortions are compensated by high-speed changes in the shape of a small, thin mirror. → wavefront; → wavefront distortion; → wavefront correction; → Strehl ratio; → tip-tilt mirror, → Shack-Hartmann wavefront sensor, → active optics.

→ adaptive; → optics.

An → adaptive optics instrument used on the → European Southern Observatory (ESO) 3.6-m telescope at La Silla. It was an upgraded version of COME-ON-PLUS, the → Very Large Telescope (VLT) adaptive optics prototype. It had 52 → actuators and performed corrections of the mirror 200 times per second. The reference → wavefront was sensed in the → visible. The observation was done in the → near-infrared (1-5 μm).

→ adaptive; → optics; → near-infrared; → system.

An → optical system that uses → adaptive optics.

→ adaptive; → optics; → system.

A branch of optics that uses coherent radiation to produce holographic three-dimensional images of objects.

→ coherent; → optics.

An → adaptive optics system with high-contrast imaging and spectroscopic capabilities. Extreme adaptive optics systems enable the detection of faint objects (e.g., → exoplanets) close to bright sources that would otherwise overwhelm them. This is accomplished both by increasing the peak intensity of point-source images and by removing light scattered by the atmosphere and the telescope optics into the → seeing disk.

→ extreme; → adaptive; → optics.

A branch of physics that deals with reflection and refraction of rays of light without reference to the wave or physical nature of light.

→ geometric; → optics.

The branch of physics that deals with the properties and phenomena of electromagnetic radiation in the wavelength range extending from the ultraviolet (at about 40 nm) to the far-infrared (at 1 mm) and with vision.

Optics, from optic, from M.Fr. optique, from M.L. opticus "of sight or seeing," from Gk. optikos "of or having to do with sight," from optos "seen, visible," from op-, root of opsesthai "be going to see," related to ops "eye," from PIE *ok^w- "eye; to see" (→ eye); → -ics.

Nurik, from nur, → light, + -ik→ -ics. Nuršenâsi, from nur, → light, + šenâsi→ -logy.

The branch of optics concerned with the wave properties of light, → diffraction, → polarization, and other phenomena for which the ray approximation of → geometric optics is not valid. Also called → wave optics.

→ physical; → optics.

The branch of optics that analyzes the electromagnetic radiation in terms of its wave characteristics. Also called → physical optics.

→ wave; → optics.