Abstract: Apparatus for rotating a sunbather's lounge chair in the sun so that the sunbather lying on the chair is exposed to the sun even while the sun direction changes from sunrise to sunset includes a sun direction detector for detecting the relative direction of the sun direct rays to the chair and produces electrical signals representative of that relative direction, the chair being carried on a rotatable platform driven clockwise (CW) or counterclockwise (CCW) as requires to position the lounge chair in the direct rays of the sun; the sun direction detector including two directional photo-detectors on the rotatable platform, held with their directions normal to generally upright planes that meet at an angle less than 180.degree., and the drive driving the platform to maintain the outputs of the photo-detectors equal or in a predetermined relationship.