Satellite telescopes such as the Hubble Space Telescope or the planned James Webb Space Telescope provide great images. But ground-based instruments continue to rival them. It is true that their view is somewhat obscured by the terrestrial atmosphere. But because they collect a lot of light with their very large mirrors, they achieve extremely high resolving power. The latest project is the European giant telescope E-ELT with a primary mirror 39 meters in diameter. Roland Gredel introduces the one billion euro instrument.
