Measuring solar disk shape up to relativistic accuracy: the role of scintillation in ancient naked eye data

TL;DR

This paper investigates how scintillation affects naked eye observations of solar and lunar phenomena, aiming to improve the accuracy of ancient eclipse data for measuring the solar disk shape.

Contribution

It introduces a method to account for scintillation effects in historical naked eye eclipse observations to enhance solar disk shape measurements.

Findings

Scintillation causes systematic differences in naked eye eclipse observations.

Venus occultations can serve as analogs for bead-like eclipse phenomena.

Historical data can be corrected for scintillation effects to improve solar measurements.

Abstract

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.