 Three tiny constellations are stacked up in the eastern evening sky this month. The arrow, the dolphin, and the little horse. There's not a single bright star among them. But under moderately dark skies, at least one of them is pretty easy to make out. The arrow is at the top of the stack. It's the third smallest of the 88 modern constellations. In ancient times, it represented a weapon used by Hercules. But there were different takes on his targets.