N-BAF10 by Schott

$$n(\lambda) = \sqrt{1 + \frac{1.58515\,\lambda^2}{\lambda^2 - 0.00926681} + \frac{0.143559\,\lambda^2}{\lambda^2 - 0.042449} + \frac{1.08521\,\lambda^2}{\lambda^2 - 105.614}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[3.79 \times 10^{-6} + 2(1.28 \times 10^{-8})\,\Delta T + 3(-1.42 \times 10^{-11})\,\Delta T^2 + \frac{5.84 \times 10^{-7} + 2(7.6 \times 10^{-10})\,\Delta T}{\lambda - 0.22}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$