Astronomy Fun Fact #98
If you look closely enough at the Big Dipper, you might notice that one of the points in the handle is actually two points. They are Mizar (the larger one) and Alcor (the smaller one), two stars that are just barely gravitationally bound to each other, but are far enough apart that they appear as two distinct points from Earth.
But you do need to have good vision to tell these two stars apart. In fact, there’s evidence that ancient groups used this as a vision test. Being able to see two distinct points was analogous to having 20/20 vision.