We were on a boat at Inland Lake stargazing. I was looking in a southerly direction at an elevation of approximately 45-50 degrees. I saw what appeared to be a single rotation of a very bright white light. It flashed/rotated once, and then about 30 seconds later I saw it again just marginally down and to the left of its original location. It reminded me of what one might see if you were to observe a lighthouse from a great distance or the rotating beacon at an airport, except that the light was quite bright and it exhibited only a singe rotation. While I have no way of verifying the height of the object, my impression was that it was very, very high in the sky. It appeared to be a very bright, powerful beacon of light (brighter than the visible stars around it) but there was no ambient light observed around me that would have been given off by the object.