Refracting telescopes use a lens to focus light. A 34-foot (10.4-meter) telescope located on La Palma of Spain's Canary Islands seized the top spot as the world's biggest ground-based optical telescope in 2009. The day before, Stierwalt had traveled from Southern California to Pingtang Astronomy Town for a conference hosted by scientists from the world’s largest telescope. The massive Thirty Meter Telescope will be able to image objects 13 billion light years away, near the beginning of time. The aperture of this reflecting telescope reaches a total 10.4 metres (34 feet) in diameter and is currently one of the most advanced in the world. The largest practical functioning refracting telescope is the Swedish 1-m Solar Telescope, which is used today for solar observations.Second is the Yerkes Observatory 40 inch (102 cm) refractor, used for astronomical and scientific observation for over a century, and the next biggest is the James Lick telescope, and the Meudon Great Refractor. Construction of world's largest optical telescope approved. The world’s largest optical telescope – to be called, appropriately, the European Extremely Large Telescope – will be built on a mountain in Chile, planners announced Monday. It can be used to explore remote planetary systems, galaxies, nebulas and black holes. Although GTC is currently the largest, plans for even larger optical telescopes are currently underway. The Extremely Large Telescope (ELT) is an astronomical observatory currently under construction.