An optical assembly includes: a first lens comprising a crown material; a second lens comprises a primary flint material for wavelengths below about 1.0 μm; and a third lens comprising a secondary flint material for wavelengths below about 1.0 μm, wherein the first, second and third lenses together are configured to transmit light and function in the visible, mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) regions of the electromagnetic spectrum. In some implementations, the optical assembly may be configured as an afocal Galilean telescope having an objective lens assembly and a eyepiece lens assembly.