2023 Update: Over the span of some 14 years since I wrote this (wow), all of the YouTube links broke. I've fixed them (except for two that sadly vanished), though you may see a "view on YouTube" message instead of being able to watch them as overlays here. I also added three more videos—two thanks to comments from Aaron and Jordan—and one I just stumbled on while searching for new links. Originally published June 10, 2009.| The Robservatory