For the coating of the steel structure, ESO opted for paints from WB Coatings (a brand of the Mipa Group since 1 January 2023). The biggest challenge in selecting the right paint was to create the deepest possible black, dull matt surface to minimise scattered light and prevent disruption during operation. With a robust epoxy primer, a PU topcoat and the matching clearcoat from WB Coatings, it was possible to fulfil the extensive requirements. Because the construction was carried out by an international consortium, the WB products were supplied to two participating companies in Spain and Italy. The individual steel components were coated there before being delivered to Chile for assembly.
When planning the steel structure, the focus was on keeping the telescope stable under all conditions, including strong winds or earthquakes. The structure must be absolutely stable to keep the components and equipment precisely aligned. At the same time, however, it must be light enough so that the gigantic ELT does not collapse under its own weight.
The ELT will have a ground-breaking optical design with five mirrors, including a huge 39 metre main mirror consisting of 798 hexagonal segments. Another mirror will adaptively adjust and correct distortions caused by air turbulence by changing its shape around a thousand times per second. The telescope is located on Cerro Armazones, a 3046 metre high mountain in the Chilean Atacama Desert. Engineers and craftsmen are currently working there to assemble the structure of the telescope dome. In the meantime, the steel dome has already taken on the round shape, which is typical for telescope domes. The six laser sources, another key component in the ELT's optical system, have now also been manufactured and delivered to ESO for testing. According to ESO, all other systems and components required for the completion of the ELT are also currently making progress in their development or production.
Construction of the ELT began nine years ago with the ground-breaking ceremony in Chile. The remaining 50% of the project is expected to be completed much faster than the construction of the first half of the ELT. The first light images are expected in 2027.
