Abstract: A fluid-containing tube is supported by a radially-disposed, heat absorbing fin so as to be coaxial with the reflective inner surface of a hemi-cylindrical reflector. Such a combination, if positioned with the reflector aperture substantially horizontal and with a North-South disposition of the reflector axis, or with the reflector aperture vertical, its axis substantially vertical and with a Southern exposure of that aperture, will produce effective sun-tracking and efficient heating of the fluid in the tube throughout the daylight hours even though the reflector remains static.