Quantify the elevation throughout yellow region!

There should be quantification of the arc values at the top and bottom of the yellow annual region. Also, you say "The closer a point is to the center, the higher is the sun above the horizon," but your graphic doesn't reflect that quantifiably. Specifically, I'd expect that at noon, an arc position of r=1/2 to be equal to 45 degrees of elevation, but it is not! Why!?! Alternatively, use your current projections, but add radius line at noon with graduations for 15, 30, 45, 60 & 75 degrees...that would be a good compromise.