A configuration for the Future Giant Telescope is proposed. It is a 30 m telescope with segmented primary mirror and alt-azimuth mounting. The aspherical f/1.2 primary mirror is made up of 1095 partial annular submirrors.The optical system includes a Nasmyth system, a coud6 system and a widefield system.

The Nasmyth system has a novel design with four mirrors and provides a ,~10 arcmin field of diffraction-limited images, a much larger field than can be obtained by the traditional Nasmyth system. Several diffractionlimited observations each over a small field, can be carried out simultaneously. By applying active optics to change the shape, tip, tilt and piston of the submirrors,thereby to effect a new aspherical surface of the primary, excellent quality images can be obtained for the coud4 system and the wide field system.

The wide field system has a field of 25 arcmin, the focal surface is only slightly curved and the atmospheric dispersion could be corrected. The tolerances of the surface

shape and position for the submirrors, and the telescope mounting and structure are also discussed. The innovations in this configuration should have a general significance for future giant telescopes.