That's a tricky question! Technically, all planets can be seen with a telescope, even the ones visible to the naked eye.

However, the planet you're likely thinking of is Uranus. It's the faintest planet visible to the naked eye, and often difficult to spot even in dark skies. A telescope makes it much easier to see and distinguish from stars.

Here's a breakdown:

* Visible to the naked eye: Mercury, Venus, Mars, Jupiter, Saturn

* Visible with a telescope: Uranus, Neptune

Let me know if you'd like more information about any of the planets!