The Blackburn pendulum is a common textbook exercise that is familiar to any student of physics, but as a senior in high school in 1967 I saw it as an artistic tool. I proceeded to make a number of simple time exposure photographs, looking up at a small neon bulb attached to such a pendulum.
For the past 8 years I have used a 3-meter Blackburn pendulum in my barn with an LED, and my camera is a large-format 4 x 5 inch sheet film camera. Working at night in total darkness, the camera looks straight up, and a time exposure is made as the LED traces out the pendulum's path. Depending on the way the pendulum is suspended, and on the particular path it is started in, the LED paints a unique image.
