Having clear skies will be integral, as the E-ELT will be expected to image big chunks of sky. Its primary mirror will measure nearly 140 feet in diameter. VLT's largest mirrors measure just under 27 feet, making E-ELT about five times bigger. The new telescope will actually gather 15 times more light than the best optical telescopes currently operating, and its images will appear 15 times sharper than those snapped by Hubble. It will be so powerful, in fact, that it will directly image rocky planets in other solar systems.