Measuring solar disk shape up to relativistic accuracy: the role of   scintillation in ancient naked eye data
  The orbital displacement of the Moon is known to a precision on the order of centimeters from the lunar laser ranging data, while the lunar profile's confidence level is still only about 200 m. The lunar motion is used to measure the solar diameter during central eclipses with accurate timing of Baily's beads at the umbral path limits. The onset or disappearance of a Baily's bead is due to the alignment between lunar limb's valleys and solar photosphere: this timing is determined outside our atmosphere. Due to scintillation, naked eye evaluations of such phenomena can be systematically different with respect to telescopes. We analyze the case of Venus' occultations as bead-like situation, in order to infer considerations on naked eye reports in historical total eclipse reports. 
Costantino Sigismondi, Richard Nugent, Gerhard Dangl
astro-ph.SR astro-ph.IM