Calculation on Asphericity of Off-axial Partial Annular Mirror

A 30m giant telescope project,Chinese Future Giant Telescope(CFGT),has been proposed by Chinese astronomers.Its primary mirror consists of 1095 off-axis partial annular aspherical sub-mirrors including 17 different types.In this paper,the method on calculating related technical parameters is considered for these sub-mirrors figuring.Their asphericities under several different constraint conditions are compared.The optimal radius of curvature of the best fitting spheres and the maximum asphericity of each type of aspherical sub-mirror are obtained.And the removals on the sub-mirror surface are plotted in 3D graphics.These calculations will be the basics of grinding and polishing these sub-mirrors in the future.