// Create an infinite sphere around scene and allow any pigment on it
sky_sphere{ pigment { gradient <0,1,0>
                      color_map { [0.00 rgb <0.6,0.7,1.0>]
                                  [0.35 rgb <0.0,0.1,0.8>]
                                  [0.65 rgb <0.0,0.1,0.8>]
                                  [1.00 rgb <0.6,0.7,1.0>] 
                                } 
                      scale 2         
                    } // end of pigment
          } //end of skysphere -------------------------------------