Working on the secondary mirror

Engineers are working on the tower of the Secondary Mirror (M2) of one of the ESO VLT 8.2-metre Unit Telescopes (UTs). The light coming from the sky is collected by the 8.2-metre primary mirror (M1), then is made to converge onto M2 and it is finally redirected to the active instrument by the tertiary mirror (M3). In order to allow the fast movements required to keep the image in focus, the 1.1-metre M2 needs to be extremely rigid and light. For this reason it has a honeycomb structure and is made of beryllium. The M2 tower is one of the most complicated mechanical pieces of the telescope. The four UTs are identical in design but each one of them is equipped with two or three highly specialised instruments. The ESO Very Large Telescope, formed by four 8.2-metre Unit Telescopes (UTs) and four 1.8-metre movable Auxiliary Telescopes (ATs), is the world´s most advanced optical ground-based astronomical facility.