Rectangular object seen in Stonehaven

Noticed an orange light 500 feet above horizon to south west. Looked like bright star that was stationary for five minutes. Came nearer to home with no noise at all. Maintained altitude at 500 feet.Object had five lights one at each corner red and orange with light to middle edge. Came forward and turned towards coastline.Banked over and shape of object was visible and was above large building so could be roughly measured for scale. Rectangular about 30ft too 50ft in diameter. Ten feet deep with two vents to rear and external superstructure of matt black pipes and slatted covers. Turned to the sea and disappeared from view.