It's almost like building telescopes is a bit easier than month-long marine expeditions.

Well I guess it's not immediately apparent. But in hindsight, the kind of telescope you need to see the moon or Uranus isn't quite the investment that a dangerous expedition to unknown lands or the bottom of the sea entails. Nor an observatory or space-bourne telescope for that matter. And you can't use a telescope to discover a continent on earth unless you were already in space.