St. Mary's grid (full) penta development.

Development of the penta system introduced in previous post.

The penta elements are coloured yellow in this set of images.

Developing the pentagonal system based on the 3by1 diagonal of the North Berwick Law orientation(in red) with St Mary's chapel as centre of the two inner circles.  The outer circle is centred on the centre of the calculated pentagon with the 3by1 diagonal from Kelso to Ericstane just north of Moffat as base side length.

The first thing of note is that the penta-chord is tangential to the inner grid circle with St.Mary's chapel at centre.  Of note also is that the northeast running radius crosses the Isle of May which is nice as I have wondered what part this island played in the geometry.

the completed penta-star.

Surprisingly the two sides of the outer pentafgon are seen to be tangential to the Bass Rock circle centred on St Mary's chapel.  The Bass Rock is not marked but is just above the 'r' in North on the crossing point of the chord on the circle circumference, but Markinch is marked on this circumference.

completion of the pentagon.

the same figure as above but with the grid system changed to green perhaps clearer.