Telescope

Telescopes were devices for looking at things from a distance.

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 is folding telescope to survey a Solonian village. (DW: The Mutants)

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)

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

In the 19th century, Robert MacLeish and Albert designed a device that others supposed was a telescope. It was in fact a light chamber. (DW: Tooth and Claw)

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)

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)