NBFD10 by Hoya

$$n(\lambda) = \sqrt{3.26156 - 0.0145429\,\lambda^2 + 0.0334707\,\lambda^{-2} + 0.00122665\,\lambda^{-4} - 2.53918 \times 10^{-5}\,\lambda^{-6} + 5.59717 \times 10^{-6}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[7.08 \times 10^{-6} + 2(1.05 \times 10^{-8})\,\Delta T + 3(-9.04 \times 10^{-11})\,\Delta T^2 + \frac{1.33 \times 10^{-6} + 2(1.07 \times 10^{-9})\,\Delta T}{\lambda - 0.00338}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$