An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

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.

Initial name given to → Vera C. Rubin Observatory.

→ large; → synoptic; → survey; → telescope.

An → optical system in which the → optical axis of the → aperture is not coincident with the mechanical center of the aperture.

→ off; → axis; → optical; → system.

1) Of or pertaining to the eye or sight.
2) Same as → optical.

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/see."

1) Nuri, nurik, from nur, → light + -i, -ik adj. suffix → -ic.
2) Didgâni, related to didgân "eyes," plural of didé "eye; seen," from didan "to see" (Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen").

The direction in a doubly refracting crystal in which light is propagated without double refraction.

→ optic; → axis.

1) Of, pertaining to, or applying optics or the principles of optics.
2) Of or pertaining to sight or vision; visual; of or pertaining to the eye.

From → optic + → -al.

→ optic.

An imperfection in the imaging properties of a lens or mirror. The main aberrations are → chromatic aberration, → spherical aberration, → coma, → astigmatism, → field curvature, → distortion.

→ optical; → aberration.

The property possessed by some substances and their solutions of rotating the plane of vibration of → polarized light. When a beam of → linearly polarized light is sent through an optically active substance, such as crystalline quartz and sugar solution, the direction of vibration of the emerging linearly polarized light is found to be different from the original direction. Those which rotate the → plane of polarization to the right, for an observer looking in the incoming beam, are called → dextrorotatory or right handed; those which rotate it to the left, → levorotatory or left handed. Optical activity may be due to an asymmetry of molecules of a substance (solutions of cane sugar) or it may be a property of a crystal as a whole (crystalline quartz).

→ optical; → activity.

The mathematical evaluation of an optical system to determine its basic optical properties and image quality characteristics.

→ optical; → analysis.

An instrument used to test lenses by utilizing the → optical transfer function. It consists of a HeNe laser, a beamsplitter and two mirrors.

→ optical; → autocorrelator.

Line passing through the optical center and the center of curvature of a → spherical mirror or → lens. Same as → principal axis.

→ optical; → axis.

A track or table on which sources, lenses, mirrors, and other optical components can be mounted and moved. It is used in optics experiments.

→ optical; bench, M.E., from O.E. benc "long seat;" cf. Da. bænk, M.Du. banc, O.H.G. banch.

Miz "table," originally "preparations for entertaining a guest; guest;" Mid.Pers. mêzd "offering, meal;" nurik, nuršenâxti, → optical.

Of a thin lens, a point situated at the geometrical center of the lens, through which an incident ray passes without being deviated.

→ optical; → center.

Any device such as a → lens, → prism, → mirror, and/or other similar objects used in an → optical system.

→ optical; → component.