Optical system for extremely large spectroscopic survey telescope

This article presents research work on a spectroscopic survey telescope.Our idea is as follows:for such a telescope,a pure reflecting optical system is designed,which should have an aperture and a field of view(FOV)both as large as possible and excellent image quality,and then a strip lensm(lens-prism)atmospheric dispersion corrector(S-ADC)is added,only for correcting the atmospheric dispersion.Given the fund limitation and the simplicity of scaling up,some 12-m telescopes are designed as examples.Su,Korsch,and Meinel put forward the four-mirror Nasmyth systems I and II,which are used in this paper.FOVs of 1.5°,2°,and 2.5°are selected.For all systems,the image qualities are excellent.Because the S-ADC relaxes the optical glass size restriction,this 12-m telescope with a FOV of 2.5°can be magnified in proportion to a 16-m telescope.Its etendue(from Frenchétendue)and focal surface will now be the largest in the world.In such a telescope,a pure reflecting optical system can also be obtained.A subsequent coudésystem is designed with excellent image quality.