Telescopes are astronomy's most important tool. Without them our picture of the Universe would be dramatically less rich and detailed.
There are many different types of telescope. Traditional ones gather visible light from distant objects to produce a magnified image. It was this kind of instrument that was first pointed skywards by the Englishman Thomas Harriot and later put to famous use by Galileo Galilei.
Image: A telescope made by Isaac Newton on display at The Royal Society
Astronomy's most important tool continues to evolve.
Dr Allan Chapman explains the instrument's development.
Sir Patrick Moore's guest Dr Allan Chapman explains the telescope's development and importance.
In 1987 Horizon reports on the William Herschel Telescope.
In 1987 Horizon reported on the William Herschel Telescope, which was built on La Palma in the Canary Islands.
Maarten Schmidt spends an evening using the Hale Telescope.
Astronomer Maarten Schmidt spends an evening using the Hale telescope at the Palomar Observatory in California. Schmidt observes quasars with the help of an assistant.
Patrick Moore looks at the William Herschel Telescope's mirror.
In 1987 Sir Patrick Moore gets a glimpse of the 4.2m mirror used in the William Herschel Telescope.
Mark Thompson gives Jonathan Ross a telescope beginner's guide.
Astronomer Mark Thompson gives Jonathan Ross a telescope beginner's guide.
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, using glass lenses. They found use in terrestrial applications and astronomy.
Within a few decades, the reflecting telescope was invented, which used mirrors. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. The word telescope now refers to a wide range of instruments detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.
The word "telescope" (from the Ancient Greek τῆλε, tele "far" and σκοπεῖν, skopein "to look or see"; τηλεσκόπος, 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".