The red and green lights were in a triangular configuration and just hovered above the airport with no sound

In approximately May of 1977 a friend of mine and I were at the Crystal Airport (MIC), Minneaplis, MN, at approximately 2300 hours local time. We had both recently received our pilot's licenses and were avid flyers.  My friend's father owned a flying school at the airport.  
We had just returned from an evening of night flying and had put the airplane in the hangar.  The night sky was very clear with stars showing brightly.  At this time of night air traffic in the Minneapolis area was very light.  During this event there were no aircraft operations at the MIC airport.  
My friend and I were talking outside at the airport and noticed some colored lights hovering in a stationary position directly above the MIC airport.  At first we thought these lights may be a helicopter, balloon, or some other type of stationary craft.  As my friend was interested in star gazing and had his telescope at the airport building, we got the telescope out to look at these lights.  We both observed, over a period of at least 10 minutes, three lights, in a tringular configuration, consisting of green and red lights, each of these being in a triangular shape, hovering directly over the airport, altitude unknown.  We believed the lights to be maybe about 10,000 feet MSL because it took the power of the telescope to clearly see them.  
The three lights appeared to "wobble" in the triangular configuration and they did not move or change altitude.  We were both very surprised that the lights, which we believed were attached to some type of solid, trianglar object, ommited no sound whatsoever.  Other than the lights, we could not actually see any type of object to which they could have been attached as it was dark night at this time.  The MIC control tower was closed at that time, so we could not contact them for confirmation of what this object may have been.  After about 10-15 minutes of observation the lights just disappeared.
Witness indicates that date is approximate.  PD