The optical system of the ELT and the role of ZERODUR®

This diagram shows the novel 5-mirror optical system of ESO's Extremely Large Telescope (ELT) and the position of the ZERODUR® mirror substrates. It is based on a giant main mirror which combines 798 hexagons (M1) and four smaller mirrors (M2 to M5) as reflectors. The main mirror collects light from the night sky and reflects it on a smaller mirror, the M2, at four meters in diameter. This in turn reflects the light to a reflector (M3) placed in the center of the M1. The task of this third mirror is to irradiate the light onto an adaptive optics (M4) placed above it, which changes its surface a thousand times a second and thus straightens the distorted starlight again. Finally, the light reaches the fifth mirror (M5), which in combination with M4 forms a built-in adaptive optics system to allow extremely sharp images to be formed at the final focal plane.

The shown graphic was updated on May 30, 2017. At this date SCHOTT has been awarded the contract to provide the substrate components for the main mirror (M1) of the ELT.
The optical system of the E-ELT and the role of ZERODUR®