C4-R Limiting Magnitude

Last night I split my first"real double", actually the triple of Zeta in Orion. I saw(with Averted Vision) the 10th mag third star, even better, I did not know it was there until I kept looking and looking. 10th magnitude isn't bad considering I live 3 blocks outside of Chicago! So I'm asking, what's the dimmest magnitude you've seen in your scopes compared to what they were rated for? According to Celestron, this scope is limited to 12mag, but what do those mathematicians know anyways!