MC-TAFD307 by Hoya

$$n(\lambda) = \sqrt{3.42861 - 0.0138453\,\lambda^2 + 0.037363\,\lambda^{-2} + 0.00118946\,\lambda^{-4} - 1.598 \times 10^{-5}\,\lambda^{-6} + 5.18274 \times 10^{-6}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[4.66 \times 10^{-6} + 2(9.63 \times 10^{-9})\,\Delta T + 3(-1.45 \times 10^{-11})\,\Delta T^2 + \frac{9.98 \times 10^{-7} + 2(8.32 \times 10^{-10})\,\Delta T}{\lambda - 0.203}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$