The Hubble Space Telescope

Hubble’s primary mirror, at 2.4 meters (about 95 inches) in diameter, is not especially large as big telescopes go.  The twin Keck telescopes have mirrors 10 meters in diameter.  However, because it is far above Earth’s atmosphere, there are no distortions.  As a result the Hubble Space Telescope can see detail equivalent to reading the date on a quarter one mile away.  

 

Shortly after Hubble was launched it was discovered that the mirror, which was accurately ground to one part in 800,000, had a systematic flaw.  So the first images were disappointing, although still better than could be achieved with Earthbound telescopes. However, optical engineers designed new lenses, sort of a new pair of “glasses” to correct the flaw, and Hubble became the most amazing instrument ever created for observing the birth, life, and death of stars and galaxies.