Thirty years ago I was told 200mm was the longest lens you could use on a hand held camera. More then that and you got camera shake or you had to add a gun stock handle to the setup.
Similar to about 7-10x power with binoculars. 30mm lens for daylight 50mm for night. Any more then that is wasted unless you have a good mount. That is from my childhood neighbor, a freighter captain
Bill D