Two telescopes to be built in Hawaii and Chile have received a technical boost from Durham University scientists who have successfully tested the ambitious optical systems intended for them.

The Gemini project involves building two eight-metre telescopes, now at the construction stage.

They aim to match the resolution of the Hubble space telescope but to concentrate on the infra red region - Hubble only covers near infra red, as well as optical and ultra violet. They will also be able to cover ten times the area of sky that Hubble can.

A key stage in developing the telescopes will be to fit them with adaptive optics. These counter the effect on the image of turbulence in the earth's atmosphere by sensing how much the image has been distorted and rapidly adjusting the shape of the mirror to correct for it. This has not been done before in the infra red part of the spectrum.

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Ray Sharples, reader in physics and Richard Myers, head of the adaptive optics programme, both from Durham University, have tested a prototype of the advanced optics system on the William Herschel telescope, a British telescope in the Canaries.

Last month they achieved very high resolution images with the system, 0.25 of an arc second, said Robert Davies, professor of astronomy at Durham University and UK project scientist for the Gemini Project.

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This result is well on the way to the goal that has been set for the Hawaii telescope, which is aiming for resolution of 0.1 of an arc second. This is equivalent to less than 100 metres at the distance of the moon, he said.