The focus ring on the eyepiece of most scopes is used to focus the crosshairs for your eyes. Kinda like a diopter setting. Look thru the scope at a white wall,focus the eyepiece(crosshairs) for your eyes,install the scope covers. That's it. You will never have to change it unless your eyes get better or worse.
It has nothing to do with the image seen in the scope(trees,animals,etc.) ---pruhdlr