Some ideas for a Large European Solar Telescope (LEST)

Dome and tube effects, instrument mount, and optics of solar telescopes are discussed, and a Gregory system is advocated for LEST. The advantages of a helium filled tube, and of a closed dome are stressed. An alt-azimuth mount is suggested. The disadvantages of active optics are pointed out. The system proposed has a composite entrance pupil formed by six circular 80 cm, apertures centered on the apexes of a hexagon, and tangent to each other. If turbulence is a problem, interferometry, using two or more of the pupils, can be applied in order to retrieve higher spatial frequencies, or the beams can be directed onto six different auxiliary instruments.