Athermal cassegrain telescope

A Cassegrain telescope design consists of a silicon primary mirror bonded into a silicon-carbide (SiC) telescope metering tube. A secondary mirror is bonded directly to the telescope window. The window sits in a SiC bezel that is bonded to the SiC telescope tube. A graphite snout is bonded to the rear of the primary mirror and extends forward into the telescope. The snout incorporates a field stop that blocks stray light and sources outside the acquisition field of view (FOV). A lens cell threads into the snout and holds two lenses that collimate the light exiting that end of the telescope.