Abstract: A seeker device, such as a seeker head, includes a housing for both a first optical assembly and a second optical assembly. In the preferred embodiment, the first optical assembly is an infrared telescope having a fixed, relatively narrow field of view for receiving incoming energy via a first path through an optical opening through the housing. The second optical assembly may be a pivotable mirror that is pivoted to provide a wide field of regard. The incoming energy that impinges the pivotable mirror enters through a second path through the optical opening. The energy from the pivotable mirror is redirected into the infrared telescope. In the preferred embodiment, the redirection is achieved by a dichroic mirror that has a high transmissivity with respect to long wave infrared energy and a high reflectivity with respect to mid wave infrared energy.