We were on roundbutte in Jefferson Co Ore, watching stars when a bright "star" appeared in the sky to the NW. It hovered for about 20 mins in a stationary position. There was a tree we could use as a gauge to monitor it's location. All of a sudden it began to move back and forth in an east to west motion. After a few mins, it moved south towards our position. As it came overhead, we got out of the car and watched it. It was very high in the atmosphere and had a triangle outline of lights. No sound came from it. There were other planes in the area and they were totally distinguishable from the triangle object. After it passed over, it headed in an easterly direction. As it moved towards the horizon, it made a "sparkling" display on the rear of the craft and then seemed to contract or shrink into itself and dissapeared. Two of us witnessed the event. It was really fasinating!