Abstract: A luminaire for luminescent light sources includes: (i) an extruded tubular `U`-shaped housing having a longitudinal external male dovetail shoulder on one side, a longitudinal external female dovetail channel on its other side, a longitudinal external female dovetail channel on the bottom, two terminating longitudinal `C`-channel tracks one along the edge of each side leg, and two diametrically opposing interior longitudinal `C`-channels; (ii) a mounting plate secured by screws received within the internal `C`-channels at each end of the housing; (iii) electrical power mounting sockets secured to the end plates; (iv) luminescent light tubes mounted in the sockets extending longitudinally within the housing; (v) a reflector surface curling around the luminescent light tubes within the housing; (vi) retractable endcaps resiliently secured by spring biased screws to each endplate closing each end of the housing; and a longitudinal curved transparent lens element having beaded side edges shaped for capture by an