Opening of the ELT secondary blank mould

Opening of the ELT secondary mirror blank mould, containing the still very hot ZERODUR® glass at first annealing. The blank was transferred from the SCHOTT melting facility to the SCHOTT 4-metre blank annealing facility in Mainz, Germany in May 2017. The casting of this mirror is a major step towards building the world’s biggest eye on the sky, one of ESO’s greatest feats.