The patch depicts the setup of a lunar eclipse; where the shadow of the Earth is eclipsing the Moon and thus preventing sunlight from reaching the latter. In our design, Earth is shown in the center; a reminiscence of the by now superseded geocentric astronomical model of the universe, with Earth at the center. Under the geocentric model, the Sun, Moon, stars, and planets all orbit Earth -- a theory that curiously doesn't impair the function of certain models, e.g. in astrolabes, where it becomes apparent that ultimately, it doesn't matter whether the Sun revolves around the Earth, or vice versa, as long as the relative relationship is properly described.
A further element of the design is the obliquity of the ecliptic, and the axis tilt of Earth at 23.44°. The symbol for the Earth is the ancient Sun cross, a modern astronomical symbol representing the Earth rather than the Sun.