Astronomical instruments

adaptive optics

Systems used with telescopes that can compensate for distortions in an image introduced by the atmosphere, resulting in sharper images.

aperture

Diameter of the primary lens or mirror of a telescope.

charge-coupled device (CCD)

Array of high-sensitivity electronic detectors of electromagnetic radiation, used at the focus of a telescope (or camera lens) to record an image or spectrum.

chromatic aberration

Distortion that causes an image to appear fuzzy when each wavelength coming into a transparent material focuses at a different spot.

detector

Device sensitive to electromagnetic radiation that makes a record of astronomical observations.

eyepiece

Magnifying lens used to view the image produced by the objective lens or primary mirror of a telescope.

focus

Point in a telescope where the rays of light converged by a mirror or lens meet.

interference

Process in which waves mix together such that their crests and troughs can alternately reinforce and cancel one another.

interferometer

Instrument that combines electromagnetic radiation from one or more telescopes to obtain a resolution equivalent to what would be obtained with a single telescope with a diameter equal to the baseline separating the individual telescopes.

interferometer array

Combination of multiple radio dishes to, in effect, work like a large number of two-dish interferometers.

prime focus

Point in a telescope where the objective lens or primary mirror focuses the light.

radar

Technique of transmitting radio waves to an object and then detecting the radiation that the object reflects back to the transmitter; used to measure the distance to, and motion of, a target object or to form images of it.

reflecting telescope

Telescope in which the principal light collector is a concave mirror.

refracting telescope

Telescope in which the principal light collector is a lens or system of lenses.

resolution

Detail in an image; specifically, the smallest angular (or linear) features that can be distinguished.

seeing

Unsteadiness of Earth’s atmosphere, which blurs telescopic images; good seeing means the atmosphere is steady.

telescope

Instrument for collecting visible-light or other electromagnetic radiation.