BACD5 by Hoya

$$n(\lambda) = \sqrt{2.48615 - 0.00956848\,\lambda^2 + 0.0146851\,\lambda^{-2} - 0.000112165\,\lambda^{-4} + 4.19788 \times 10^{-5}\,\lambda^{-6} - 1.88562 \times 10^{-6}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.09 \times 10^{-6} + 2(1.25 \times 10^{-8})\,\Delta T + 3(-4.95 \times 10^{-11})\,\Delta T^2 + \frac{5.43 \times 10^{-7} + 2(5.6 \times 10^{-10})\,\Delta T}{\lambda - 1.57 \times 10^{-9}}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$