Kamin using his telescope
Cochrane's telescope
The USS Enterprise-E viewed through a telescope
A telescope is an optical device consisting of variable combinations of lenses and mirrors that focus light, allowing for viewing of distant objects. Widely used in the fields of astronomy and surveying. Early Human configurations of the telescope were constructed by Galileo Galilei.
In 2152, when Captain Jonathan Archer spent his shore leave on Risa, he had a date with Keyla on his terrace. There he had a telescope and viewed fascinated through it until he finally directed Keyla to Earth's sun, which was about 90 light years away. (ENT: "Two Days and Two Nights")
Kamin built a telescope on Kataan that he and his daughter Meribor used often. (TNG: "The Inner Light")
Henry Starling kept a telescope in his office at the Chronowerx tower. (VOY: "Future's End")
Rain Robinson once confessed to Tom Paris that the reason why she became an astronomer was because of her brother, who "had a telescope, a little refractor. You could barely see in the tree house next door actually, but it was enough to see the rings of Saturn." All she ever wanted since was to "reach up and touch them." (VOY: "Future's End, Part II")
Zefram Cochrane used a reflecting telescope to view the USS Enterprise-E in orbit around Earth in 2063. (Star Trek: First Contact)
In 2154, the Syrrannites used telescopes to discover three Vulcan cruisers over the Forge, ready to attack their compound in the T'Karath Sanctuary. (ENT: "Awakening")