Optical design method of two-mirror astronomical telescopes with reduced misalignment sensitivities based on the nodal aberration theory

Abstract

This paper proposes a systematic design method for two-mirror astronomical telescopes with reduced misalignment sensitivities. The analytic expressions between misalignment sensitivities and optical structure parameters are derived based on the nodal aberration theory (NAT). The sensitivities include coma and astigmatism aberration to lateral misalignments. The inherent relations among different misalignment sensitivities and conditions when optical structure parameters satisfy zero misalignment sensitivities have been summarized. On this basis, the design method is introduced. The design method gives consideration to both reduced misalignment sensitivities and good image quality, which utilizes monotonicity of the misalignment sensitivities functions. To demonstrate further the feasibility of the design method, an example for the Ritchey-Chretien (R-C) telescope is conducted. The results show that misalignment sensitivities can be reduced effectively.