Why is the ninth month called September?
1640s, from Italian telescopio (used by Galileo, 1611), and Modern Latin telescopium (used by Kepler, 1613), both from Greek teleskopos "far-seeing," from tele- "far" (see tele-) + -skopos "seeing" (see -scope). Said to have been coined by Prince Cesi, founder and head of the Roman Academy of the Lincei (Galileo was a member). Used in English in Latin form from 1619.
"to force together one inside the other" (like the sliding tubes of some telescopes), 1867, from telescope (n.). Related: Telescoped; telescoping.
A device used by astronomers to magnify images or collect more light from distant objects by gathering and concentrating radiation. The most familiar kind of telescope is the optical telescope, which collects radiation in the form of visible light. It may work by reflection, with a bowl-shaped mirror at its base, or by refraction, with a system of lenses. Other kinds of telescopes collect other kinds of radiation; there are radio telescopes (which collect radio waves), x-ray telescopes, and infrared telescopes. Radio and optical telescopes may be situated on the Earth, since the Earth's atmosphere allows light and radio waves through but absorbs radiation from several other regions of the electromagnetic spectrum. X-ray telescopes are placed in space.