This is an illustration — two illustrations, actually — from A New Astronomy for Beginners by David P. Todd. It’s actually an illustration of a demonstration, with a nattily dressed young man holding a disk, representing the Moon’s orbit around the Earth, at arm’s length, with his eye representing the Sun. Sort of complicated on paper. Seems like it makes more sense in person, maybe?
But at least we can picture it, along with some primo 19th-century men’s fashion.
It’s just one of the marvelous illustrations in this book, which you can peruse here, on Archive.org.