In Pursuit of Starlight:

The easiest method of studying light from a cosmic object is to collect it through a telescope and record it on a photographic plate. photographic plate are exposed for long periods of time-sometimes night after night-to  the light being collected by a telescope aimed at distant stars. Since the Earth rotates on its axis, the stars appear to move  in  the sky. The telescope  is  rotated  following  the  daily movement of  the  stars at which it is aimed. Thus, its movement  is synchronised with the movement of  the stars being studied, stars, far too faint for human eyes, slowly begin  to register on the plate. This method of collecting and investigating light from the cosmos is called optical astronomy. Over the centuries, astronomers have refined the telescope from the first crude lenses of Galilee's day  to giant 'telescopes in  use  today. Three  simple pieces of  glass, the  lens, the mirror and  the prism  over the period  of a  few hundred years. have  turned  into sophisticated  and  powerful  tools  in  human hands. Shouldn't  we  marvel at  the  ingenuity of the  human mind'? As of today, a huge optical telescope called the Hubble space  telescope. after Edwin IIubble, is in orbit around the earth. Several large telescopes are stationed  in the USA, Hawaii, Australia, Chile, Russia, U.K.  etc.