The smallest ELT mirror is a big challenge | ELT Updates

The ELT’s M5 mirror blank has been completed. M5 is the smallest mirror on the telescope, but it has a big task: through a tip-tilt system, it can adjust its position to compensate for atmospheric turbulence and other factors, and yield extremely sharp images. To do this without breaking, the mirror blank needs to be very stiff and very lightweight at the same time — and made of a special material, which you can discover in this video. 

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