Hi James,
The reason for the magnitude limit is that this is roughly the detection limit of my TV system (Watec 902H2 Ultimate + 3.8mm, f/0.8 lens) in individual video frames. Deeper limits are possible with TV systems using longer focal lengths but you then get smaller fields of view.
The frames are analysed using a program called UFO Analyser. This matches stars in the image with a catalogue (see the image below) and then uses this to estimate the magnitude of the meteor throughout its path. The magnitude quoted is the maximum magnitude but the advantage of a TV system is that you can get a magnitude profile sampled 25 times a second.
Nick.
