September - The ELT’s M2 mirror blank

Displayed here is the massive 3-tonne blank for the Extremely Large Telescope’s (ELT) secondary mirror, M2. To create a mirror for a telescope, a mirror blank is cast and then polished and coated to form a finished mirror.

This particular mirror was successfully machined by the German company SCHOTT and will be the largest secondary mirror ever employed on an optical telescope. A truly remarkable example of pioneering optical engineering, the mirror and its support system will hang upside-down above the 39-metre primary mirror of the ELT.