A suggested 12-m telescope optical system configuration for China

• Published in: Monthly notices of the Royal Astronomical Society 2016-08, Vol.460 (2), p.2286-2295
• Main Authors: Su, Ding-qiang, Liang, Ming, Yuan, Xiangyan, Bai, Hua, Cui, Xiangqun
• Format: Article
• Language: English
• Subjects: Adaptive optics; Astronomy; Exchange; Image quality; Infrared imaging systems; Infrared telescopes; Optics; Secondary mirrors; Space telescopes; Spectrographs; Spectrum analysis; Symbols; Telescopes
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stw1064

This is an optical/infrared telescope. It is a general purpose telescope. A segmented primary mirror is adopted with diameter 12 m and f-ratio 1.6. This telescope has prime focus, Cassegrain, Nasmyth and coudé systems. The prime focus system has a 1 $_{.}^{\circ}$ 5 field-of-view corrector with excellent image quality. It will be used for multi-object fibre spectroscopic observation and CCD photography. In this 12-m telescope, all systems except the prime focus system share the same secondary mirror; the Nasmyth and coudé systems are formed by adding relay mirrors; and the method of moving a secondary mirror is used to enhance image quality. All these features originate from the innovative optical system of the Chinese 2.16-m telescope. At the Cassegrain focus, a dark object spectrograph, for example, can be installed without any corrector; and in case a field of view is needed, a corrector may be added. Both the Nasmyth and coudé systems have exceptionally excellent image quality and the exchange between them occurs very conveniently. Many instruments in visible and infrared wavebands, some with an adaptive optics system, will be installed at the Nasmyth platform. Coudé system will be used for interferometry and for those instruments which require high stability. This configuration has a nearly full range of systems but it is not complex, and it can even be adopted by 20–40-m class telescopes.