A telescope is a tool that astronomers use to see faraway objects most telescopes and all large telescopes work by using curved mirrors to gather and focus light from the night sky the first telescopes focused light by using pieces of curved clear glass called lenses so why do we use mirrors today. A telescope is an optical instrument used to magnify and enhance the view of faraway objects be they astronomical or terrestrial most telescopes fall into one of two main categories refractor or reflector also available are schmidt cassegrain telescopes a combination of reflector and refractor. All about telescopes telescopes help us to see far distances the first telescope was invented in the early 1600s in the dawn of the scientific revolution before then people had to rely on the naked eye