Abstract: A cylindrical metal tube is provided with an outer transparent jacket, the jacket being spaced apart from the tube by bushings at each end and sealed therewith by means of o-ring type elastomeric seals positioned in grooves in the bushings. The intermediate space between the tube and the jacket is evacuated through a side tube on the jacket to reduce heat loss from the surface of the tube due to convection of air. The solar energy collector tube of this invention is applicable to flat plate type collector installations as well as concentrating collectors such as those employing parabolic trough reflectors. The flow path of the heat transfer fluid is straight through the tube, affording simple manifolding of multiple solar energy collection tubes arranged in parallel to span a specified area of collection.