When the sun is not normal to {HEAD ~ the plane} containing {TAIL ~ the cannister}, the near cannister is shaded from direct sunlight and the far cannister is exposed 
When the sun is not normal to { HEAD ~ the plane } containing { TAIL ~ the cannister } , the near cannister is shaded from direct sunlight and the far cannister is exposed
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH