You should have been around when HID cannister lights with NiMH battery packs first became popular. Cylindrical objects with wires attached, obscurred by a heavy layer of shrink wrap, now that made going through airport security loads of fun (try explaining why HID bulbs should not be turned on out of the water, or why you should leave it burning for a few minutes prior to turning it off.)
greeeat, I'm heading south in Feb. Guess I should contact the local airport to see what sort of hassels I can expect from them when I show up with a cannister light, regs etc for carry on. Maybe taking some papers with a description of the items and the manufacturers website will help a bit?
I think the only thing that would help is going after someone else in your group and let them deal with it Once they figure out that an HID light is not a nuclear warhead detonator and that multiple ones don't click together to make one then you should be fine.
I really wish they had something like that, where you could get your stuff preapproved or whatever. At least have it tagged at the original airport as containing scuba gear or something, so that it won't be such a big deal at each security check point.
Another thing to remember is that you cannot travel with liquids in your carry on luggage ~ Like your compass, for example. Remember to pack that in your checked luggage, or you'll lose it!
Also, if your can light is in your carry on, you can go to the website (of whatever make your light is), and print out the owner's manual/description of your light. It helps to have that tied around your light.
Your compass does not have enough liquid inside it to be a problem. Acording to the TSA you can have 3 ounces of liquid. I know the liquid in the compass is not that much. I fly with my compass in my carry on every time.
If you do have a concern, you can always put it in your checked luggage...if you dare.