a black triangle. thought i saw 3 stars, but then they started moving together in the same direction. then noticed the 3 points was the corner of the aircraft because the in between them, they would block out other stars. it was big. maybe over rio vista area, or oakley but just very slow. almost could not tell it was moving. it might have been in space, but then it would be realy big. not sure of altitude or distance. i was on my side yard when i saw it, just looking at the stars, and their it was flying. then after bout 2 min it changed direction to the north and the points faded out. lasted about 5 min in all. tried to get my wife but it was gone by the time we got back out.