MC-TAF401 by Hoya

$$n(\lambda) = \sqrt{3.07279 - 0.0136638\,\lambda^2 + 0.0252735\,\lambda^{-2} + 0.000612182\,\lambda^{-4} - 1.14704 \times 10^{-5}\,\lambda^{-6} + 1.543 \times 10^{-6}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[5.9 \times 10^{-6} + 2(8.91 \times 10^{-9})\,\Delta T + 3(-2.46 \times 10^{-11})\,\Delta T^2 + \frac{7.38 \times 10^{-7} + 2(5.77 \times 10^{-10})\,\Delta T}{\lambda - 0.164}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$