Bright fan shaped light which quivered and shimmered, finally swirling and vanishing.we saw a strangely formed light in the southern sky, below and west of the moon. The sky was dark enough to just make out stars. The object moved from left to right and appeared to have a tail of light in a distinct fan shape behind it. The fan shape appeared to have a mist or vapor in the light, which quivered or shimmered and which was very bright. We stopped the car and turned off the engine but there was no sound (country road and very quiet). The fan of light swirled and slowly dissipated and there was no further sign of anything. It was certainly not a star, airplane, or helicopter. The evening was completely clear with good visibility and no cloud.((Vandenberg rocket launch. PD))