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The control system is an essential and important part of an astronomical telescope. For large telescopes, an efficient control system is vital for successful observations. In this paper, an exhaustive study of generic models of control systems for large telescopes and a wide range of their common requirements are presented. This paper also discusses a basic hierarchical structure, workflow model, and telescope control model based on object-oriented analysis, as well as the main data flow model of a general purpose telescope. After analysis of these models, a layered and orthogonal architecture, which has a wide range of adaptability, is proposed. The design of a concrete architecture based on the message bus, which is used in the LAMOST (Large Sky Area Multi-Object Fiber Spectroscopy Telescope) project and FAST (The Five-Hundred-Meter Aperture Spherical Radio Telescope) project, is discussed. The design of the control systems proposed in this paper can serve as a useful reference in the construction of large telescopes.

Bi-substituted rare-earth iron garnets, (REBi)3Fe5O12 (REBiIG), are used in wide-band optical communication as Faraday rotators in an optical isolator. However, the influence of rare-earth ions on the magneto optical (MO) properties of REBiIG crystals, such as specific Faraday rotation (FR) and coercive force, is not clear. The aim of the present work is to compare the MO properties of garnets doped with different rare-earth ions. REBiIG (RE=Ho, Yb, or/and Tb) crystals were grown from Bi2O3 self-fluxed melts by the top-seeded solution growth method under the same conditions. It was found that both specific FR and coercive force decrease with an increase in rare-earth ion radius. The FR wavelength stability of HoYbBiIG is better than that of YbBiIG but worse than that of HoBiIG. However, the FR temperature stability of HoYbBiIG is worse than that of YbBiIG but better than that of HoBiIG. It is noted that HoYbBiIG crystal is a trade-off between HoBiIG and YbBiIG crystals in terms of MO properties.