How were the circles drawn?

[Jorge_Stolfi]

Small thread on how the Rosette folio roundels were made:
The Voynich Ninja > Voynich Research > Imagery > Some comments upon the construction of the circles of the Rosettes You are not allowed to view links. Register or Login to view.

Thanks!

For general amusement and edification, here is an annotated clip off69v showing some of the defects in the circles:

   

Anomalies in the circles and text ring baselines of f69v. (C1,C2,C3) correct traces of circles C1, C2, and C3, which are invisible in some places.  To be compared with the white overlay lines, which are geometric circles concentric with those traces but smaller by ~0.5 mm all  around. (E2,E3) Deviant traces of circles C2 and C3. Note that they run vaguely parallel to the correct traces for some distance, after missing them. (S1,S2,S3) Baseline corrections (full or partial) of text rings R1, R2, and R3, after they get past the wrong traces of C2 and C3, and adjust to the correct traces.