ESO DOI Service

• Vernet, Elise [European Southern Observatory (ESO)]
• Cirasuolo, Michele [European Southern Observatory (ESO)]
• Cayrel, Marc [European Southern Observatory (ESO)]
• Tamai, Roberto [European Southern Observatory (ESO)]
• Kellerer, Aglae [European Southern Observatory (ESO)]
• Pettazzi, Lorenzo [European Southern Observatory (ESO)]
• Lilley, Paul [European Southern Observatory (ESO)]
• Zuluaga, Pablo [European Southern Observatory (ESO)]
• Diaz Cano, Carlos [European Southern Observatory (ESO)]
• Koehler, Bertrand [European Southern Observatory (ESO)]
• Biancat Marchet, Fabio [European Southern Observatory (ESO)]
• Gonzalez, Juan Carlos [European Southern Observatory (ESO)]
• Tuti, Mauro [European Southern Observatory (ESO)]
• The ELT Team [European Southern Observatory (ESO)]

The Extremely Large Telescope (ELT) is at the core of ESO’s vision to deliver the largest optical and infrared telescope in the world. Continuing our series of Messenger articles describing the optical elements of the ELT, we focus here on the quaternary mirror (M4), a true technological wonder; it is the largest deformable mirror ever made. In combination with M5, M4 is vital to delivering the sharp (diffraction-limited) images needed for science by correcting for atmospheric turbulence and the vibrations of the telescope itself. Here we describe the main characteristics of M4, the challenges and complexity involved in the production of this unique adaptive mirror, and its manufacturing status.