Observational Astronomy
Basic observational astronomy presents an interesting paradox. On one hand, there are only a few very bright objects in the sky: one Sun, one Moon, five visible planets, fifteen bright stars, and about fifteen easy-to-find constellations.
Yet most people can't name more than one or two constellations, and many even have difficulty describing how we see the moon cycle. The reason students don't permanently grasp the patterns is that celestial bodies constantly move according to daily and seasonal patterns.
Falling Apple's basic astronomy course eliminates this confusion by starting with a simplified 2D version of the sky, where everthing is related to the Sun (see Sun, Moon & Planets).
Step two expands the model by introducing the stars and constellations (see The Stars).
The third and final step expands the 2D model to include 3D effects (see Seasons & the Celestial Sphere).