Reflector 74 is {TAIL ~ a parabolic arc} of which {HEAD ~ the focus} is also at 76, but the axis 80 of the parabola makes with the horizontal an angle α equal to the maximum solar altitude: the directrix of arc 74 is at 81, and makes with directrix 77 an angle equal to the supplement of angle α 
of
Reflector 74 is { TAIL ~ a parabolic arc } of which { HEAD ~ the focus } is also at 76 , but the axis 80 of the parabola makes with the horizontal an angle α equal to the maximum solar altitude : the directrix of arc 74 is at 81 , and makes with directrix 77 an angle equal to the supplement of angle α
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL REL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH