Illustration of the changing M_BH constraints in NGC 1453 as the orbit model goes through the step-by-step axisymmetrization procedure described in Sections 3 and 4. The starting case (red dotted) uses the original code with typical (near) axisymmetric parameters assumed in the literature (ψ = 90.°001; see Section 5.1 for details). The end case (black solid) uses our final axisymmetrized code including all changes from Sections 3 and 4. The four intermediate curves have all of the code fixes described in Section 4, but have different combinations of orbit types according to Sections 3.2 and 3.3. The left panel is for models with orbital weights chosen by fitting to the first four Gauss–Hermite moments of the LOSVDs determined from kinematic data, as is typical in the literature. The right panel uses 12 moments as constraints and shows tighter constraints on M_BH, as is reported in Liepold et al. (2020). The 1D χ² in M_BH is obtained by marginalizing over the stellar mass-to-light ratio using a smoothed 2D χ² landscape generated by Gaussian process regression with a squared-exponential covariance function (Pedregosa et al. 2011). The dark matter halo is fixed to the best-fit logarithmic halo in Liepold et al. (2020).