ESO Special: Seeing Sharp
Date- 10th May 12 Source- http://www.eso.org/public/videos/archive/category/esocast/ 'The third special episode of this series -- ESOcast 43 overall -- presents ESO's flagship facility: the Very Large Telescope (VLT). In this episode we discover the state-of-the-art technology behind this telescope, which has provided astronomers with an unequalled view of the Universe. To obtain the sharpest images of the sky, the VLT has to cope with two major effects that distort the images of celestial objects. The first one is mirror deformations due to their large sizes. This problem is corrected using a computer-controlled support system — active optics — that ensures that the mirrors keep their desired shapes under all circumstances. The second effect is produced by Earth's atmosphere, which makes stars appear blurry, even with the largest telescopes. Adaptive optics is a real-time correction of the distortions produced by the atmosphere using computer-controlled mirrors that deform hundreds of times per second to counteract the atmospheric effects. As one demonstration of its power the VLT's sensitive infrared cameras, helped by adaptive optics, have been able to peer through the massive dust clouds that block our view to Milky Way's core. The images, taken over many years, have allowed astronomers to actually watch stars orbiting around the monstrous black hole that lies in the center of our galaxy. It was even possible to detect energetic flares from gas clouds falling into the black hole.'