Hubble Space Telescope
When the HST took its first pictures, astronomers were happy to see the images, but they were not as sharp and as crisp as expected. Telescopes in space can take better pictures than telescopes on Earth, but for some reason, the pictures were not better than the pictures taken on Earth. They found a problem with the telescope's mirror. The mirror was not curved right. It was only wrong by 2.2 microns (1/50th as thick as a piece of paper). Still, this was enough to cause the images to be blurred. Some said that Hubble was nearsighted.