Structural thermal optical performance tradeoffs in monometallic Cassegrain telescopes with varying telephoto ratio

Structural thermal optical performance (STOP) analysis is applied to Cassegrain telescopes utilizing architectures in which all components are fabricated from one metal. The goal is athermalized performance via uniform thermal expansion. For each telescope design, the telephoto ratio of total track length to effective focal length (EFL) is varied by adjusting total track length. The remaining system level parameters of effective focal length, aperture ratio, and field of view are maintained by adjusting curvatures and conic constants appropriately. An increase in sensitivity to temperature variations is observed with decreasing telephoto ratio. This demonstrates a fundamental tradeoff between package size and sensitivity to temperature variation, or equivalently, inhomogeneity in coefficient of thermal expansion.