Telescope

A Telescope is an optical device that enables the observation of distant objects. The first practical telescopes were produced in Holland in the early 17th Century Known as refracting telescopes they used glass lenses to focus the light.

In 1609 Galileo became the first ever person to observe celestial objects with a telescope. The word ‘telescope’ is derived from the Greek for ‘far-seeing’ and in 1611 was coined by Giovanni Demisiani for one of Galileo’s instruments.

In 1668 Isaac Newton built the first practical reflecting telescope which used highly polished mirrors to focus light. The design of the refracting telescope was improved in 1733 with the invention of the achromatic lens and this enabled the making of shorter, more functional telescopes which became widely used in the Navy and for other military purposes.

The 20th century has seen many different types of telescopes invented including radio and infrared telescopes and the term is now used for instruments that detect different areas of the electromagnetic spectrum.