6: Astronomical Instruments

Question 1

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

Answer 1

interferometer array

Question 2

(of telescope) point where the rays of light converged by a mirror or lens meet

Answer 2

focus

Question 3

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

Answer 3

eyepiece

Question 4

light in a telescope is reflected by a small secondary mirror off to one side, where it can be detected

Answer 4

Newtonian focus

Question 5

concave metal reflector in a radio-reflecting telescope, analogous to a telescope mirror

Answer 5

dish

Question 6

instrument for collecting visible-light or other electromagnetic radiation to observe distant objects

Answer 6

telescope

Question 7

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

Answer 7

seeing

Question 8

device sensitive to electromagnetic radiation that makes a record of astronomical observations

Answer 8

detector

Question 9

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

Answer 9

chromatic abberation

Question 10

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

Answer 10

interference

Question 11

length of time that a lens collects light before creating an image

Answer 11

integration time

Question 12

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

Answer 12

radar

Question 13

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

Answer 13

adaptive optics

Question 14

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

Answer 14

charge-coupled device (CCD)

Question 15

telescope in which the principal light collector is a concave mirror

Answer 15

reflecting telescope

Question 16

light in a telescope is reflected by the secondary mirror down through a hole in the primary mirror to an observing station below the telescope - used in most professional telescopes

Answer 16

Cassegrain focus

Question 17

diameter of the primary lens or mirror of a telescope

Answer 17

aperture

Question 18

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

Answer 18

refracting telescope

Question 19

transparent piece of material that bends the rays of light passing through it

Answer 19

lens

Question 20

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

Answer 20

prime focus

Question 21

modern technology that measures sag on a telescope mirror and applies force to its back to correct it

Answer 21

active control

Question 22

piece of material with thousands of grooves on its surface that spreads light out into a spectrum

Answer 22

grating

Question 23

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

Answer 23

resolution

Question 24

distance from the lens to the location where the light rays focus behind the lens (image)

Answer 24

focal length

Question 25

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 separate telescopes

Answer 25

interferometer