Make: Technology on Your Time Volume 34

Solar OBSERVATORY

How I fashioned a low-tech setup to record the sun’s movement.

By Craig Van Horn

Originally, I just wanted to make a fancy sundial. My idea was that instead of projecting a shadow on the dial face, I would set up a lens and project a bright circular image of the sun instead. Also, I wanted the dial face to be big, so the lens had to have a long focal length. I wanted to follow the sun during the winter months when its path tracks lowest and closest to the horizon, and to have enough accuracy to see the daily change in its altitude as the days got shorter, then longer again starting around December 22.

My house has a south-facing ...