January 31st will be a busy day in the sky, as three skygazing events are occurring together. First, there’s a total lunar eclipse—the first time the moon has been completely immersed in Earth’s shadow since September 27-28, 2015. Second, this event falls on the second full moon of the month, what’s often called a blue moon. And, third, the eclipse comes just 27 hours after the moon reaches its closest orbital point to Earth, called perigee.