Left: as a function of surface gravity, the top panel shows the value of the primary fixed point, μ₁, for the linear plus square root parametrization, for spherical atmospheres of varying effective temperature. The bottom panel shows the dependence of the normalized V-band intensity of the fixed point. Red fiilled circles are T_eff = 3000 K, green open squares 4000 K, blue open circles 5000 K, magenta downward pointing triangles 6000 K and pale blue upward pointing triangles are 7000 K. The black crosses show the behavior of the fixed point from the grid of plane-parallel model atmospheres for comparison. Right: as a function of effective temperature, the top panel shows the fixed point, μ₁, and the bottom panel shows the dependence of the V-band intensity of the fixed point. Red triangles represents models with log    g = 0, green squares log    g = 1, and blue circles are log    g = 2. Again, black crosses represent the fixed point from plane-parallel model atmospheres.