Wide angle mirror system design for distortionless imaging of the sky.

We describe a dual-mirror wide angle optical design, which removes the radial distortion associated with traditional all-sky optics for a chosen altitude. The wide angle mirror system provides a transform of the sky, for a selected altitude, as if the viewer is situated at the center of the Earth. Other advantages of the system include (1) real time achromatic transform, (2) higher optical gain compared to pure lens systems, (3) a quasi-telecentric optic capable of taking narrowband interference filters without modification, and (4) a uniform sky spatial resolution everywhere on the detector. Disadvantages include (1) cost of manufacture and (2) focusing issues, especially near the horizon.