Reflective astronomical telescopes with a large field of view and a wide wave band.

Abstract

Large-aperture ground-based astronomical telescopes are expected to have a large field of view (FoV) and a wide working wave band. We design two coaxial reflective telescopes based on a low-order even asphere and a high-order Q-con polynomial. Both telescopes have a primary mirror with a diameter of 6.5 m, a focal length of 24 m, and a working wavelength that stretches from ultraviolet to near-infrared (0.365-2.4 µm). The telescopes using an asphere and a Q-con polynomial have spectroscopic-survey fields of 3° and 3.4°, respectively. In these fields, the EE80D (diameter of 80%-enclosed light energy) values that can characterize the telescope image quality is less than 0.58'', and the spectral data can be obtained using fibers at the focal surface of the telescopes. Additionally, the two reflective telescopes can image celestial targets in a 0.4° FoV, and the root mean square diameters of the standard spot diagrams are less than 27 µm. By combining precise imaging measurements with the spectral data, the properties of celestial bodies can be better analyzed. The designed telescopes could enable the realization of astronomical spectroscopic surveys with both a large FoV and a wide waveband.