When mirrors exceed 8 meters (26 feet) in diameter, they are no longer rigid enough to maintain the same shape when they are tilted. The Keck I telescope was the first to be built of 36 hexagonal mirrors. The tilt of each mirror is controlled electronically so that they all focus their light rays at a single point. The electronics can position each corner of the mirror to an accuracy 4 nanometers to create the final image. Constructing the telescope of multiple smaller mirrors greatly reduced the cost of the telescope. The Large Binocular Telescope consists of the Keck I and Keck II 10-meter (33-foot) telescopes. When they are used together they can detect the interference of light from a star and thus determine its size and location much more precisely.
The Hubble Space Telescope can see deeper into space than earthbound telescopes because there is no atmospheric distortion to interfere with how it sees images.