Originally posted by Escape81
Hmmm . . .Now, I may be mistaken - but after the lightsaber duel was over, and Sidious was disarmed [literally], he told Luke that he was done with the "Jedi dueling games" and then he prepared a Force Storm.
So, after just having his hand removed and being bested in combat, he still had enough time to prepare a Force Storm while his enemy [Luke] was in range to kill him.
So, we must deduce, that it is easily under a minute and only a few seconds. I doubt that is enough time for Luke to kill Kyp and Sidious.
THat's assuming Luke doesn't kill Sidious first or chunks him into a star.