The images that you are generating from my simple formula. in the p , h plane are fascinating ; perhaps you can do a similar treatment using these parameters. top left X 0.0025031289111390 y 0.8188647746243739 bottom right x 1.9949937421777222 y -0.6755031853255635 ----- vhpp.par ------------- test { reset=2004 type=formula formulafile=fractint.frm formulaname=V-HeunPH center-mag=0.998748/0.0716808/1.338358 float=y maxiter=2048 inside=bof61 outside=0 logmap=yes colors=@blues.map } --------- end par ------- I wasn't expecting the p , h plane ,to be overly complicated , however you can never tell when fractals are involved. The next step is to take the V-HeunPH values and use them with V-Heun. Using the vhpp.par file we obtaim a type of curve that's at the boundary between the unstable outside and the ultra stable inside ; values from this region are what I may initially use for V-Huen , however your explorations are suggesting other possibilities.