Current concept for the 4m European Solar Telescope (EST) optical design

The European Solar Telescope (EST) is a 4-m class solar telescope to be located in the Canary Islands which is currently in its conceptual design study. EST is a pan-european project (with 29 partners, plus 7 collaborating institutions, from 14 countries) promoted by the European Association for Solar Telescopes (EAST). In the current concept, the main telescope and its transfer optics assemblies 14 mirrors to provide a Science Coude Focus with an F/50 telecentric beam. It is diffraction-limited in a FOV of 1 arcmin with an unvignetted FOV of 2'x2'. The whole system is being optimized in throughput for several instruments observing simultaneously in a spectral range from 0.39 mu m to 2.3 mu m. Its innovative concept integrates an optical transfer stage assembling multiconjugated adaptive optics with optical field de-rotation and with a perfect balance of the whole system in terms of polarization being also time and wavelength invariant.