On Thursday, Sept. 25 -- Two days before the Harvest Moon peaks, the lunar disc is already blinding.

its last stop before turning fully lit on Saturday, when the Harvest Moon takes over the night sky. For a brief window each evening, the disc looks so nearly full that casual observers may already mistake it for the real thing.

But the mathematics still says otherwise. Full Moon arrives on Saturday, September 26 at 12:49 p.m. EDT - 16:49 UTC - when the lunar surface reaches precisely opposite the Sun as seen from Earth, according to NASA. Tonight the Moon is about two degrees short, close enough that the naked eye finds no gap, but precise enough that lunar photographers will see the shadow edge still creeping westward along the terminat...