This simple heliostat uses a small reflecting telescope diagonal flat
mirror for the sun tracker's "primary", mounted to a small magnet for easy removal.
The inset shows the .25" aperture (not optically round due to the angle of incidence), made from a post-it piece and paper hole punch,
to increase sharpness in the same manner that stopping down a lens increases
depth of field. The melamine base provides a flat surface for smooth
turning of the polar axis and is separated by a credit
card blank "washer".
The "focal length" of the system was about 44' or f2112. The sun's image,
approximately 5" in diameter, was projected onto white paper, the final image
was projected on coated paper and exhibited almost no "hot spot".
Photos were taken using a tripod that was moved several times
to get closer to the axis of projection, hence the
slightly different shapes of the sun's image.
The third sun frame shows a less sharp image with post-it aperture removed thus making a larger aperture (the whole mirror) of about 1" x .75" ( ~f603).
Sun spots are easily visible in several frames. A utility wire and partial cloudiness
are seen in the frames near the end. Weather was generally clear with slight haze.
The final sun frame was taken the following day with a 1/8 in. aperture at 48 feet (f4608) made from mounted black paper placed close to but after the sun tracker mirror. The third photo shows the setup of this smaller, black paper aperture.
All photos (c) 2002, Ron Gross.