Teorie lunari, effemeridi e sistemi di coordinate (Lunar theories, ephemerides and coordinates systems)

TL;DR

This paper compares French and US ephemerides to analyze the lunar shadow during the 2006 solar eclipse, exploring lunar theories, geodesy, and the impact of ephemeris differences on eclipse predictions.

Contribution

It provides a detailed comparison of lunar ephemerides and their effects on eclipse shadow calculations, linking historical lunar theories to modern observational applications.

Findings

Differences in ephemerides affect the predicted extent of the umbral shadow.

Use of lunar center of figure versus center of mass causes discrepancies.

Results supported observational measurements of the solar diameter during the eclipse.

Abstract

This work deals with the comparison of different parameters (French/IMCCE and US/JPL ephemerides) used to calculate the extension of the umbral shadow and the location of the centre line in the total solar eclipse that took place on March, 29th 2006. We needed to know the exact points where the predicted duration of the solar eclipse was 0 seconds. This phenomenon allows, observed on this particular position, the measurement of the solar diameter. The work is composed by three parts. In the first one is described the evolution of the lunar theory from Hipparchus to the current theory (Bureau de Longitudes/IMCCE, Chapront). The second part is dedicated to geodesy (WGS84 datum) and there are examples of longitude's calculations. In the third one there is the analysis of the parameters to understand the reasons about the different extensions of the umbral shadow and the different positions of the centre line in the solar eclipse calculated respectively with French and American ephemerides. The use of the center of the figure of the Moon with respect to the center of mass produces the differences in the ephemerides. This work prepared the observational mission in Egypt to observe the total solar eclipse from the shadow's edges in Zawayet al Mahtallah, near Sidi Barrani, whose results were after published in Solar Physics vol. 259 p. 189 (2009).