Bluish green object moving up and down over a lake.On vacation, checking sky after seeing what appeared as two campfires at 12 midnight. At 3 AM, the fires were no longer seen but I saw one bluish green object going up and down in the sky. It moved about and then paused over the lake. From my bed, I watched the object. It never changed shape or color. It appeared to jump from one position to another very quickly,