Abstract: A solar energy collecting device includes a rotation axis to be mounted parallel to the earth's polar axis, a solar energy collector mounted for rotation around the rotation axis at a predetermined rotation speed, the solar energy collector defining a tilt angle with respect to the rotation axis, and a tilt angle adjustment mechanism for automatically and intermittently adjusting the tilt angle. Various configurations of the solar energy collector are possible, and the rotation speed may be one revolution per day or half a revolution per day depending on the solar energy collector configuration. Many drive modes are possible, including rotating continuously throughout a day or rotating during daylight hours and rotating backward or forward at night. The tilt angle adjustment mechanism includes a handle fixed to the solar energy collector and a tilt angle change guide.