Astro/Zodiac symmetry on recto/verso

[Jorge_Stolfi]

I was surprised recently with how much symmetry exists between the recto and verso sheets in zodiac and astro.

Good observation!

The circles in the Zodiac and other round diagrams were drawn with a compass.  One can see in the images the pinprick created by the pointy leg of the compass.  (On the transmission-light Multi-spectral images one can even see that it is indeed a hole).

So presumably the Scribe, when he drew the diagram on the second side of a folio, just placed the compass in the same hole that he created while drawing the first side.  

And indeed, when I was looking for the pinpricks on the diagrams, I never noticed two separate holes.  

As for the nymphs and other details being aligned across the vellum:  if the two diagrams have the same number of things (say, both six or both eight), the alignment is almost inevitable.  Ditto if one number is a multiple of the other.  And many diagrams are divided into 4, 8,or 16 sectors -- which are the easiest to get, even though the Scribe did the division by hand rather than with the compass.  (The Scribe apparently did not know how to use a compass to divide a circle into 6 equal parts, or to divide any angle into two equal parts.  And a division into 5, 10, or 20 parts, which he needed for the Zodiac diagrams, would not have been closer to his abilities than quantum chromodynamics.)

All the best, --stolfi