A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light). The first known practical telescopes were invented in the Netherlands at the beginning of the 17th century. The word telescope can refer to a wide range of instruments detecting different regions of the electromagnetic spectrum.
The word "telescope" (from the Greek, tele "far" and skopein "to look or see"; teleskopos "far-seeing") was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galilei's instruments presented at a banquet at the Accademia dei Lincei. In the Starry Messenger Galileo had used the term "perspicillum". (wikipedia)