Telescope

Telescopes were devices for looking at things from a distance. "Spyglass" was a name sometimes applied to handheld telescopes. (MA: The Empire of Glass)

On Dulkis, the Second Doctor was about to view some ruins with his folding telescope when Jamie McCrimmon took it from him. He then returned it after using it to examine the ruins. (DW: The Dominators)

On Solos, the Third Doctor used his folding telescope to survey a Solonian village. (DW: The Mutants)

The Sixth Doctor used a fixed telescope aboard Voyager's "Death-ship" to follow Astrolabus's escape. (DWM: Voyager)

The people of Sarn used telescopes. Peri Brown made use of a fixed telescope in order to search for the Fifth Doctor. (DW: Planet of Fire)

Early astronomers used telescopes to look observe the stars and planets. In Alexandria a group of astronomers saw skyships. (DWM: Voyager)

In the late 15th century, Giuliano developed a primitive telescope, which the Fourth Doctor deemed merely adequate. (DW: The Masque of Mandragora)

In the early 17th century, Galileo Galilei invented the telescope. (MA: The Empire of Glass)

Richard Dunbar told the Fourth Doctor that if he had seen anything like the Krynoid pod before, he must have a very powerful telescope. (DW: The Seeds of Doom)

On Pluto, the Fourth Doctor used a folding telescope to admire the a city and noted it to be "an engineering achievement". (DW: The Sun Makers)

Jerome Weismuller used a folding telescope to watch for a satellite. (DW: Delta and the Bannermen)

Eugene Jones used a telescope to watch for aliens. (TW: Random Shoes)

Wilfred Mott had a telescope, which he frequently used. (DW: Partners in Crime) In an alternate timeline, he offered to sell it for extra money, but Donna Noble was firmly against it. (DW: Turn Left)

The Fourth Doctor used a telescope to locate the Jagaroth ship in Earth's primordial past. (DW: City of Death)

The Fourth Doctor later used the same telescope to observe the spaceship Hydrax from afar. (DW: State of Decay)

On Kirith, the Seventh Doctor used a telescope to survey Kirith town and its environs. He then gave the telescope to Miríl. (NA: Timewyrm: Apocalypse)