The Extremely Large Telescope

UK involvement in the ELT


  • One of the most challenging areas for the telescope construction will be in the manufacturing and integration of the optics.
  • The primary mirror is 39.3m in diameter and consists of 798 hexagonal segments of 1.45m wide and only 50mm thick.
  • The optical design is based on a novel five mirror scheme that delivers exceptional image quality.
  • The hexagonal geometry of the primary mirror segments permits the use of a common support structure. The segment and segment support form the segment assembly. The assembly is moved in position and tip-tilt by three position actuators. Inductive edge sensors are used to give direct position feedback to the actuators and for global reconstruction of the overall mirror shape.
  • To make maximum advantage of the site and latest advances in technology and instrumentation the E-ELT will be an adaptive telescope.
  • The fourth mirror of the optical design will be a thin deformable mirror capable of compensating for the fuzziness of stellar images created by atmospheric turbulence. With almost 6000 actuators the mirror shape can be corrected at a thousand times per second.