Hi Philippe,
Looking at your Flickr portfolio, I suspect there is more you can tell me about photography than the other way around, but here goes.
As we are, stricktly speaking, panning a whole lot as aviation photographers I am going to assume you specifically mean panning with a slow shutter speed. I am certainly no expert at it, as most of the time I do not seek its effect (if conditions make it possible at all). I generally don't want my take-offs or landings to look like they're doing 700mph if you know what I mean, that is not the impression I want to convey. That said, panning long exposures can create great visual effects, and it can turn a distracting background into an exciting one as well.
Based on my limited experience, it depends on both the situation and your equipment what works best. I tend to think two factors play a main role:
- the heavier the gear you're using, the more useful support can be;
- the lager the pan angle (how many degrees do you swing the lens), the less practical support is.
This paints a range between hand-held panning with a light camera set over large angles and using a tripod for a heavy set over small angles.
Obviously, the main advantage of support is it helps to reduce vertical shake. The main disadvantage is you sort of have to step around your mono- or tripod while panning, hence the second factor above. I suspect that matches your experience of feeling late to capture the action. It's a different movement. This is worse with a tripod than a monopod of course.
On the other hand, the monopod tends to tilt while you're turning and so will your camera, because having it on a loose ballhead on a monopod results in very awkward handling. On a tripod it's the contrary, you need to have the ballhead loose but - and this may be its main advantage here - you can hold the body with both hands even with heavy lenses, like a gunner if you will. This greatly helps keeping the horizon level and the movement smooth. On a monopod I need one hand on the lens if it's a heavy one, in order not to loose the set's balance.
It may well be that good hand-held shooting techniques do as much as using support. Take a steady attitude, find out if having the lens support turned upwards works better for you than having it below the lens when holding it (you likely know all this). Very important, even with short exposures, anticipate in what direction(s) you will be shooting and 'unwind' your body. Start with a twist in order to look more or less straight ahead at the most important point, usually where the angular velocity is the highest as well - especially in this case.
-- As I had the reply window open, Flyboy replied as well, with useful tips. Not sure if 'heavy' should be taken literally there. And indeed, few keepers...
Either way, I hope anyone chips in who has more/other/better info!
Cheers,
Erik