Imaging - Limiting magnitude

Folks - just curious as to what limiting magnitude(s) folks are finding with their imaging setups.

I'm guessing that the key factors are:

Aperture
Imager (QE)
Inherent sky brightness (light pollution and bright objects - the Moon)
Air mass (location of object)

I'm sure other factors also come into play (collimation, focus, optical quality, baffling...)

Tonight, I managed a confirmed mag 18.7 asteroid.

14" SCT
PL1001E CCD
Poor to medium light pollution, no Moon

In the past, I've managed a confirmed mag 17.9

8" SCT
Meade DSI
Poor to medium light pollution, no Moon

What are other folks getting?

Cheers
Dave

Hi Dave! I know trevor durity did a test to see what the visual limiting mag. in salthill is! he found it out to be either 3.5 or 4.5! :shock:
The amount of high power beams here is ridiculous!