Palpatine raised his spidery arms toward Luke: blinding white bolts of energy coruscated from his fingers, shot across the room like sorcerous lightning, and tore through the boy’s insides, looking for ground. The young Jedi was all at once confounded and in agony—he’d never heard of such a power, such a corruption of the Force, let alone experienced it. But if it was Force-generated, it could be Force-repelled. Luke raised his arms to deflect the bolts. Initially, he was successful—the lightning rebounded from his touch, harmlessly into the walls. Soon, though, the shocks came with such speed and power, they coursed over and into him, and he could only shrink before them, convulsed with pain, his knees buckling, his powers at ebb.--Taken from Return of the Jedi
Luke never deflected the force lightning in the film. He immediately went down. This isn't canon.