* Refracting telescopes (the type you might picture in your head) use a convex lens as their primary objective lens to gather and focus light from distant objects.

* Reflecting telescopes use concave mirrors as their primary light gatherer, but they may still have convex lenses used in the eyepiece or other parts of the telescope's optical system to further focus the light.

So, while not all parts of a telescope use convex lenses, they are a fundamental component in the design of many telescopes.