Patent ID: 7130127

Claim:
A terrestrial telescope with a digital camera comprising: a group of objective lenses having an optical axis; an image pickup device disposed along the optical axis of the group of objective lenses at a position at which an image is formed by the group of objective lenses; a quick-return half-mirror inserted into the optical axis and at a rear side of the group of objective lenses so as to be retractable from the optical axis during imaging; and an observation optical system for observing an optical image reflected by the quick-return half-mirror; wherein the quick-return half-mirror has a transmission surface having a single-eccentric toroidal configuration with different curvatures in vertical and horizontal planes of the quick-return half-mirror for correcting the position on the image pickup device at which the image is formed so that the position on the image pickup device at which the image is formed remains substantially unchanged regardless of whether the quick-return half-mirror is inserted into or retracted from the optical axis of the group of objective lenses.