Design Solutions for Dome and Main Structure (mount) of Giant Telescopes

During the last recent years, designs for several giant telescopes ranging from 20 to 40m in diameter are being developed: European Extremely Large Telescope (E-ELT), Giant Magellan Telescope (GMT) and Thirty Meter Telescope (TMT).It is evident that simple direct up-scaling of solutions that were more or less successful in the 8 to 10m class telescopes can not lead to viable designs for the future giant telescopes. New solutions are required to provide adequate load sharing, to cope with the large-scale derived deflections and to provide the required compliance, or to respond to structure-mechanism control interaction issues, among others.From IDOM experience in the development of the Dome and Main Structure of the European Extremely Large Telescope and our participation in some other giant telescopes, this paper reviews several design approaches for the main mechanisms and key structural parts of enclosures and mounts/main structures for giant telescopes, analyzing pros and cons of the different alternatives and outlining the preferred design schemes.The assessment is carried out mainly from a technical and performance-based angle but it also considers specific logistical issues for the assembly of these large telescopes in remote and space-limited areas, together with cost and schedule related issues.