ITS REASSURING to know that an engineering screw-up doesnt always get you into trouble. It can sometimes even dig you out of it, as astronomers found out at the Canada-France-Hawaii telescope on Mauna Kea, Hawaii.

In early 2003, researchers began observing the skies using the telescope, equipped with a new digital camera - the biggest in the world at the time. The CFHT was fitted with four precision lenses so the camera could capture crisp images of vast areas of sky.

The results were disappointing. The images were sharp in the centre, but far more blurred than expected at the sides. Various tests failed to find a problem, much less a solution, so astronomers pressed ahead with a five-year survey using the camera, until May 2004, when a steering committee said the image quality was jeopardising the project.

A laborious investigation followed, with engineers dismantling the optics and reassembling them daily, but finding no answer. Then one day, an engineer mistakenly replaced one of the four lenses back-to-front. The images improved spectacularly.

"The next observations were just Wow!," says Christian Veillet, the observatorys director. "The image quality was just what it should have been."

To this day, no one understands why the back-to-front lens works so well, or why it didnt work when it was oriented as planned. "That has been frustrating, but it would be a waste of resources to investigate, so we decided to just forget about it," says Veillet. "Now the science that is coming out is exquisite."

Im still wondering why it worked the second way, guess we will never find out though.

[shout] Steve! [/shout]