A system that I have used that I haven't read about before.
For the scope point of aim. The cross hair divides the field of light into 4 quadrants. The top left quadrant comes to a point in the bottom right corner of the top left field of light or the top left intersection of the cross hairs. This quarter of light will give the shooter a view of 1/4 of the smallest target visible. 1/4 of a gnats eye is visible with enough magnification. The top left point is chosen because of the long distance right hand drift (600 + yards) of a bullet due to pitch and yaw of the pill due to RH twist and the earths rotation. For normal hunting distances the drift doesnt come into play. Heavy cross hairs are easiest to see in low light and this gives an infinitely fine point of aim.
Next is the target. Take a box and place a sheet of BLACK paper in the bottom . Mark the corners so another sheet of paper can be located exactly. You will be looking into the top of the open box. Have a large hole in the center of the bottom of the box. Put a small hole in the BLACK paper, 1/8, 3/16, 1/4 etc.
When you are looking at the target, you are looking at a point of light. With the top left corner of the cross hairs as the aim point and a point of light as the target you can get a much more definite point of aim. The higher the magnification the more the light through the target hole will effect things. You can see the light rays bend as the cross hairs are moved around on the point of light. I hope this makes sence to someone.
It works well for me. eddiegjr