I'm a photography enthusiast, and a firearm enthusiast.. I'd like to think I'm reasonably informed.. But if someone climbed out of a car, near an airport , and started "aiming" that contraption at airplanes..
I'D have wonder what was happening, even if I were just a few yards away. Imagine the poor tower guy who spots it via binoculars from 3/4 mile :o
He's GOING to call some sort of security to come see what you're up to (and don't be surprised if it's with guns drawn

)