Tests have begun on one of the world's largest optical telescopes, installed on a mountain in the Canary Islands.
The GTC sits above the clouds on a high peak on La Palma
Situated on a 2,400m-high (7,900ft) peak on the island of La Palma, the huge telescope consists of a mirror measuring 10.4m (34.1ft) in diameter.
The Spanish-led Great Canary Telescope (GTC) is extremely powerful and will be able to spot some of the faintest, most distant objects in the Universe.
The GTC team expect the telescope to be fully operational within 12 months.
The enormous array has taken seven years to construct; its installation has been hampered by poor weather and the logistical difficulties of transporting equipment to such an inaccessible location.
The project is estimated to cost 130m euros (£88m).
Based at the Roque de los Muchachos Observatory, the optical telescope is made up from 36 separate hexagonal mirror segments which together form the 10.4m primary mirror.
Its vast size will enable it to capture some of the most distant light in the Universe, helping researchers look for information that might help to explain the evolution of the cosmos.
It will probe far-off galaxies, look into the secrets of star formation, and hunt for Earth-like planets.
"It would be wonderful if this telescope allowed us to detect a planet like ours," project director Pedro Alvarez told the Spanish El Mundo newspaper.
Campbell Warden, the executive secretary of the Canary Islands Astrophysics Institute, told BBC News: "The big advantage of the GCT over existing telescopes... is that because of the combination of the very advanced technology and the largest optical infrared mirror we'll be able to characterise the atmospheres of planets, instead of just having, as we have at the moment, mathematical speculations of what planets could be like.
"We'll actually be able to take a much better look at them."
He added: "We'll be able to throw back the curtains that shroud the early Universe, revealing many of its mysteries."
The GTC is among the world's largest optical reflecting telescopes.
The newly opened Southern African Large Telescope (Salt) boasts a segmented primary mirror with - in the longest dimension - a diameter of 11m (36ft).
The Hobby-Eberly on Mount Fowlkes in Texas, US, also has an 11m mirror; however, the way that it works means the Keck twins in Hawaii, which have mirrors 10m (33ft) across, have a slightly larger light-collecting area.
The Salt has a mirror that is 11m in diameter
The twins can also be made to work in tandem - as a so-called interferometer - which allows them to mimic a larger telescope that is 85m (279ft) wide.
These US scopes are rivalled in power by Europe's own Very Large Telescope, sited in Chile, which includes four large mirror units (each 8.2m across) that will soon also be made to work as one.
When they do this, the VLT will mimic a telescope that is 200m (650ft) across.
The Large Binocular Telescope in Arizona, US, uses two 8.4m (27.6ft) mirrors side by side to achieve an effective 11.8m (38.7ft) diameter.
All of these scopes will be dwarfed in the next decade if plans are progressed to build facilities with mirrors that are 30-60m (100-200ft) across.