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Published online by Cambridge University Press: 19 July 2016
Today even for the most efficient spectrograph combined with a large telescope the light efficiency is only about 0.01 to 0.1 for spectral resolving power R larger than 10000 in optical wavelength band (OWB). Consequently for a very high signal to noise ratio spectral observation of rather bright stars still needs very large telescope. The main reason is that there are too many optical surface with rather low light efficiency and serious light loss at the limited slit width. In this paper we suggest a very high efficiency telescope-spectrograph system which will give an overall light efficiency varied from 0.21 at 400 nm to 0.44 at 700 nm, four fold higher than before. Using this system for R = 100000, S/N larger than 100 the limiting magnitude will be about 15.