World's biggest telescope project approved The European Southern Observatory has approved construction of what will be the world's largest optical telescope, to be located on a mountaintop in Chile. Artist's impression of the the European Extremely Large Telescope (E-ELT). Credit: ESO GARCHING, Germany, June 11 (UPI) -- The European Southern Observatory has approved construction of what will be the world's largest optical telescope, to be located on a mountaintop in Chile. ESO member states approved the project at a meeting in Germany Monday, the BBC reported. The European Extremely Large Telescope will have a primary mirror around 130 feet in diameter, and will be built in Chile's Atacama desert region to take advantage of the area's extremely arid conditions, conducive to excellent astronomical observation, officials said. Although the telescope has been approved, there is still the matter of its $1.2 billion in funding, which has not been fully secured. That could happen by the time of the ESO's next meeting in December, when Brazil is likely to have become the 15th full member of the organization, spreading the telescope's cost and making it more affordable for member nations. The telescope is intended to be complete and ready to begin astronomical observations in 2022.