Jupiter hides its moons.

If you were out observing late Wednesday night, September 2 and you just happened to point your telescope at Jupiter, you might have been surprised at what you saw or, more to the point, what you did not see. This was a very rare case of all of the 4 of Jupiter's Galilean moons - Io, Europa, Ganymede and Callisto NOT being visible in a telescope or binocular. Unfortunately, I did not see it as I was recovering from a sinus infection, but Bob, my fellow astronomer here at OpticsPlanet, did. Bob now has the honor of claiming that he witnessed a sight that won't be visible, again, according to Astronomy.com magazine until 2019. With any luck at all, I will not have another sinus problem until after 2019.