The Very Large Telescope (VLT) at Cerro Paranal, Chile, is moving closer to full operation, with the third of four unit telescopes achieving first light in January. Polishing of the mirror for the European Southern Observatory's fourth and final unit telescope was completed in December, and that mirror is scheduled to be delivered to Chile by April.
When all four telescopes are in operation, they will be able to observe individually or to be combined to work as one for interferometry. Together they have 12 focuses, instruments for observing wavelengths from 300 nm to 25 µm, and a variety of spectroscopic modes that will allow astronomers to look at objects ranging from single stars to star-forming regions to clusters of galaxies. The VLT is also equipped with an active optics system to cancel out atmospheric disturbances.
The fourth 8.2-m mirror was polished by the optical department of the SAGEM Group (Paris, France) to a precision of 8.5 nm, giving an optical resolution of 0.03 arc sec in the visible spectrum, making it the most accurate in the world.