From: John D. Howard
Date: 2017 Jul 29, 19:03 -0700
I draw the lines at the height of my eye so it is the scope height.
I never worked it out untill your question. My spot is about 200 feet from the different horazontial lines. The mirror is 3 inches from my scope so there is about 4.3 minutes of arc difference. I had always subtracted 4 minutes as a personal dip. Now I know why.