Knothole camera obscura and total solar eclipse

As a child I lived on a farm. A round tree knot of board fell out of the wooden door of the dark hallway and on a sunny day on the chalk-whitened wall one could see an inverted image of our yard in a circle of light. In fact, it was a camera obscura. One day, in a static image, I was surprised to notice some kind of slow movement: it was my grandmother walking across the yard. And then on July 31, 1981, when a total solar eclipse occurred, a round sunspot on the wall turned into a crescent, which is forever etched in my memory.