Abstract: An infrared motion sensing apparatus mounted within the canopy of a decorative lighting fixture where the apparatus may be vertically adjusted. The apparatus comprises a pyroelectric infrared sensor located in a stationary base. Mounted over the sensor and movable in a vertical direction is a Fresnel lens array. The array is mounted to a frame that is constrained to ride on the base in a vertical direction in response to the rotation of a screw. The canopy has an opening to allow radiation to be received by the sensor and a second opening for a stem of the screw so that manipulation of the stem may take place without disassembly of any part of the lighting fixture.