JuliaData[c_, {{xmin_, xmax_}, {ymin_, ymax_}}, xdiv_, ydiv_] :=
Table[orbitLength[x + I y, c], {y, ymax,
ymin, -(ymax - ymin)/ydiv}, {x, xmin, xmax, (xmax - xmin)/xdiv}]
data = JuliaData[-.1 + 8 I, {{-2, 2}, {-2, 2}}, 100, 500];
ArrayPlot[data, DataRange -> {{-2, 2}, {-2, 2}},
FrameTicks -> Automatic]