Exclusively horizontal Fresnel effect

Before I describe my situation I want to say that I do know how the fresnel node works. I’ve reproduced it here since I need to tweak it to do what I want.

My problem is that fresnel only outputs a single float, which describes both the vertical and horizontal factors of the effect. My question is how can I create a fresnel effect that only outputs to the horizontalness. So for the output, I need a 0-1 float (0 being looking at the surface straight on and 1 being looking at the surface completely horizontal).

I think I mentioned this but how up or down your view is to the surface shouldn’t affect the output.