<< Graphics`ContourPlot3D`
phi[x_, y_, z_, a_, b_, c_] = 
        1/Sqrt[(x - a)^2 + (y - b)^2 + (z - 
                    c)^2];
a = 
      Table[
ContourPlot3D[
          phi[x, y, z, -t + 10, 0, 0] + phi[x, y, z, t + 10, 0, 0], {x, 
            8, 12}, {y, -1.5, 1.5}, {z, -1.5, 1.5}, 
          PlotPoints -> 5, Contours -> {2}, 
          PlotRange -> {{8, 12}, {-1.5, 1.5}, {-1.5, 1.5}}], {t, 
          1.5, 0.5, -0.15}
]
b = 
      Table[
ContourPlot3D[
          phi[x, y, z, -t + 10, 0, 0] + phi[x, y, z, t + 10, 0, 0], {x, 
            8, 12}, {y, -1.5, 1.5}, {z, -1.5, 1.5}, 
          PlotPoints -> 5, Contours -> {2}, 
          PlotRange -> {{8, 12}, {-1.5, 1.5}, {-1.5, 1.5}}], {t, 
          0.5, 1.5, 0.15}
]
c = Append[a, b];
SetDirectory["c:\\"];
Export["b.gif", c];