FD60 by Hoya

$$n(\lambda) = \sqrt{3.11715 - 0.0116163\,\lambda^2 + 0.044865\,\lambda^{-2} + 0.00165885\,\lambda^{-4} + 2.57169 \times 10^{-5}\,\lambda^{-6} + 1.47577 \times 10^{-5}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-5.29 \times 10^{-6} + 2(9.6 \times 10^{-9})\,\Delta T + 3(-5.1 \times 10^{-11})\,\Delta T^2 + \frac{1.06 \times 10^{-6} + 2(1.34 \times 10^{-9})\,\Delta T}{\lambda - 0.282}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$