Parameters specifying the expansion of the surface in sperical harmonics.

• ahfinder::ahf_lmax
  The maximal number of terms in the expansion in $\theta$. The default value is 8. The maximal value is 19.
• ahfinder::ahf_phi (steerable)
  If axisymmetry is expected the surface does not need to be expanded in phi. This is the default. To look for non-axisymmetric surface use ahf_phi = "yes".
• ahfinder::ahf_[xyz]c (steerable)
  Sets the x-, y-, and z-coordinates of the center of the expansion. The default is the origin (ahf_xc = 0, ahf_yc = 0, ahf_zc = 0). The center of the expansion should be set inside the expected apparent horizon, otherwise the algorithm will fail.
• ahfinder::ahf_wander
  The center of the expansion can also be allowed to move. To do this use ahf_wander = "yes". However, this only works with the minimization algorithm. The default is for the center not to move.
• ahfinder::ahf_r0 (steerable)
  Sets the radius of the initial sphere. The default is 0.0, forcing the largest sphere possible in the grid.