I want to understand how dawnbreaker's unique enchantment works on undead. Specifically, what is the highest leveled enemy I can turn, and how long does the turn effect last for? I would also like to know if taking the necromage perk gives a boost to either of the turn effects magnitude or duration. Thanks in advance to anyone who can answer my questions.

The http://www.uesp.net/wiki/Skyrim:Dawnbreaker page should help you out.

Thanks for the help. I checked this page a few weeks ago but missed this part: "The fiery explosion has the same visual effect and functions the same way as the http://www.uesp.net/wiki/Skyrim:Bane_of_the_Undead spell."