In what branch of science is telescope the most important tool?

Такой прибор как телескоп известен каждому школьнику. Нетрудно догадаться, инструментом какой науки он является. 

Every science has a set of different methods and tools to make great discoveries and inventions. One of the most amazing sciences studying the world is Astronomy. It is a science about the Universe. And a telescope is a perfect equipment to improve our knowledge about stars, planets, comets and galaxies. The device allows to observe remote objects. A lot of scientists use it in their researches.