Shadows are created when a source of light is blocked. Obvious, right? Also obvious is the brighter the source, the easier it is to see the shadow cast. So you might wonder, how faint an object can you use as a light source and still be able to detect a shadow?We know the Sun and Moon cast shadows, and Venus is well-known for this as well. The entire sky is bright enough, even at night, to throw shadows under the right
conditions. But what about the next brightest light source in the night sky: Jupiter? There have been claims for decades (I found one from 1905!) but I’ve never seen any proof.Canadian “amateur” astronomer Laurent V. Joli-Coeur wondered about this as well. So he set about dreaming up a way to do it: build a rig that would allow him to set up a “Jupiterdial” — like a sundial, with a gnomon (a post) that would cast a shadow, but which he could aim at Jupiter — and take a time exposure on his camera.