When shooting over really long distances the rotation of the earth will move the target away from the original location you were shooting at. Sounds complicated? We've made a simple, low-cost and effective solution for this as well. Coreolis is a very minor but real effect. However minute the correction, if a simple glance will show you a solution why not take it? The alternative is a certain miss.
This was mostly a pet project to demonstrate innovation, but we will build a few copies for those interested. You need to shoot well past 1200 meters for this to have any practical value.