ARMATURE: Near PHI Aspect Ratio (1.618) (13/8=1.625). I would like to use this size in the field more often; not too large and not too small. but very close to my favorite size's aspect ratio, 1.6 (10x16). In fact 8 and 13 are part of the Fibonacci Series, 1,1,2,3,5,8,13, 21, ... The focal point was designed to be at the upper right polar point, the 'eye' of the spiral. A secondary focal point can be seen near the upper left polar point (if the spiral were superimposed).
More information about the PHI Armature.