Optical system research of multi-object fiber spectroscopic survey telescope

Abstract

Abstract In the first part of this paper, four different Cassegrain optical systems with their correctors are designed and studied for multi-object fiber slit spectroscopic survey. The aperture in 6.5 m and field of view 3° are taken for these optical systems. Assuming observation wavelength range is 0.365–0.95 μm, the maximum zenith distance for observing is 60°, the maximum diameter of these lenses is 1.66 m, the altitude of the telescope site is 2500 m, two correctors are composed of 4-piece lenses and the other two are 5-piece lenses. The results obtained are: f-ratio about 3.7, the image quality for all four systems with EE80D ≤ 0.60″, the linear diameter of the focal surface is about 1.2 m and 11 000 fibers can be set on it. Considering the limit of size of fused silica and optical glass, the maximum diameter for lens is about 1.7 m. Such a 6.5 m telescope is about the largest one if using the above correctors. Considering the multi-object spectroscopic survey is greatly important, we also studied some telescope optical systems having their aperture near or larger than 10 m used for the multi-object fiber spectroscopic survey. Such ideas are introduced in the last section of this paper.