A Shooting Chrony Alpha Chrony chronograph can measure velocities for air guns and firearms, including powerful firearms. Now you can test your air gun"s velocity yourself! All Chrony models are powered by a single 9V battery and can be easily attached to a 1/4-20 tpi camera tripod for fast, easy set up. The Chrony is simple to use, just unfold the box, set the sky screens in place with the diffusers, turn on the switch and start shooting. The Velocity stays on display until you shoot again. One String, from 2 to 32 shot memory (Numbered) Measures High, Low and Average Velocities, Extreme Spread and Standard Deviations.