The more I look at this, I think the Aubrey Circle was intentionally designed in Indus Feet (IF), not Imperial Feet. You yourself gave the clue. I have a geometric proof...or I should say I have the geometric relationship which explains this better with Indus Feet than with Imperial Feet. It also makes more astronomical sense. As shown the proof works for either metric, Imperial or Indus at Sarsen.
As to your observation: The diagonal of the Great Pyramid in Indus Feet relates to the Aubrey Circle in inch by the factor 11/10 x 10.
622.25 rc x 1.562 IF/rc = 972 IF [Note I am using 100/64 to convert from royal cubits to Indus Feet]
972 IF x 11/10 x 10 = 10,692 inch = 810 IF = 891 imperial feet, which is what Thom determined.
Here is how this works out geometrically. I looped out 27.5 to purify the geometry away from the monuments. All numbers are divided by 27.5, with 27.5 thus set to unity.
This is what you are actually doing by that operation: You are taking the diagonal, converted to IF, and multiplying it with 5/6 x 11/10 x 12.
5/6 gets you directly from the diagonal 972 IF to the Sarsen circle, 810 in IF.
But what is the Sarsen Circle in IF? It is really 10 times a 9x9 square which relates to an 8x8 square as shown in the illustration. 64, fortuitously, is both surface and perimeter. 64 is a special number in geometry.
What is the significance of 64/81? it's the ratio of an inscribed circle to its surrounding square.
Now, you can think of the Sarsen Circle as 10x the perimeter of a square, whose inscribed circle is the perimeter of the Great Pyramid reconfigured in cubit units of 27.5. By converting this to IF, you are converting 64 to 100, i.e. the decimal system. Converting to 81 in IF gives you 6417/64 x 100 = 126.5625 IF2
126.5625 is 1/10 of a Sarsen Cycle in IF
1265.625 x 10 /(100/64) = 810 [you have to take out the cubit to Indus Foot conversion again you previously added or else the circle is numerically larger than it actually is.]
11/10x12 converts the Sarsen Circle from IF to Imperial feet and from Imperial feet to inch, but this is unnecessary. In reality, 11/10 x 12 is just 13.2. You are really just converting IF to inch directly.
So why does the Aubrey Circle make more sense in IF than in Imperial Feet? Because whoever watched the period of the Moon may have concluded that it's closest to 27 whole days, not 28.
Here is one way the Stonehenge builders may have tracked the Saros Cycle:
Each one turn of the Aubrey Circle is 30 months of 27 days.
After each one turn, you back up 13 days/13 IF and count them again: That's 823 days per cycle and it begins anew.
Repeat 7 more times: 8 x 823 = 6584 days
On the first day of the ninth cycle, it's Eclipse Day = 6585 days.
It's almost too easy.
Edited 2 time(s). Last edit at 17-Jul-18 06:08 by Manu.