Astronomers in Chile said this week they had created the world's largest virtual optical telescope by using a special technique to combine images from the four most powerful devices as if they were a single device.

"This weekend we managed to finish the process (of merging the images) after almost a year," said Jean-Philippe Berger, a scientist at the European Southern Observatory which operates the Very Large Telescope array (VLT) in Chile's high northern desert

"For the first time, we made scientific observations through this new instrument, and we can say that it can be used."

The VLT complex in Paranal includes four large optical telescopes, each of which are about 30 meters (100 feet) high and have mirrors eight meters (25 feet) in diameter.

The astronomers brought together the signals received by the four telescopes thanks to a technique known as interferometry, which combines the images from the four to achieve a higher resolution image.

This creates a virtual mirror which is the equivalent of 130 meters (400 feet) in diameter and, according to Berger, improves the resolution and the ability to "zoom" in on the cosmos.

"We see the surface of stars, including objects that have never been observed before, such as some very young stars or galaxies," Berger explained.

"It is very difficult to build large optical telescopes, so interferometry was used," he added. "We have been working on this for a long time and are very excited to start doing science" with it.

The complex is operated by the ESO, created in 1962 and which has support from Austria, Belgium, Brazil, Britain, the Czech Republic, Denmark, Finland, France, Germany, Italy, the Netherlands, Portugal, Spain, Sweden and Switzerland.