The ideal horizon does not exist unless the seas are flat. If the seas are not flat then you are in a trough or on top or somewhere in between. With practice and from the same location on your boat you will take the horizon somewhere on the wave(or boat motion). This consistency can only come from use and practice but it works. If your time taking is also consist ant you can get a reasonable LOP(within 5 to 10 miles). Not bad when you are still out 500 miles. I know that the electronics will be much closer as long as they do not go down but I consider a sextant as the ultimate redundant system for crossing larger bodies of water.. Regards. Leonard Stern, Indifference.