Hi Brett,
I was doing some novae, using lenses from 50mm to 1000mm mounted on my Canon 400D and IRIS (software,
http://www.astrosurf.com/buil/us/iris/iris.htm).
The magnitude 12 was not a problem at all (with 1000mm MTO), even from Melbourne's light polluted skies.
However, equatorial mount and reasonable tracking (up to 30 sec) is essential here.