An optical system including a first lens group configured to correct for lateral chromatic aberration, and an adjacent second lens group configured to correct for axial chromatic aberration. The optical system includes a detector disposed behind the second lens group, a mechanism for switching the optical system between a narrow field of view configuration and a wide field of view configuration, and a ray path steering system including a pair of counter-rotating grisms disposed in front of the first lens group. The optical system also includes a stabilization system configured to suppress image jitter and including a mechanism for decentering at least one lens in the first or second lens groups orthogonal to an optical axis of the optical system. A pupil of the optical system is located external to the first and second lens groups for location of a cold shield within a cryo-vac Dewar enclosing the detector.