Hubble Essentials

BackLight Path through Hubble

When light strikes the concave primary mirror of the Hubble Space Telescope, it is reflected to the convex secondary mirror, then back through a hole in the center of the primary mirror. There, the light comes to the focal point and passes to one of Hubble's instruments. Telescopes of this design are called Cassegrain telescopes, after the person who designed the first one.