Astrometry and relativity II: Solar grazes & solar diameter
The occasion of a central solar eclipse can be exploited to measure the solar diameter up to 0.01 arcsec of accuracy, individuating the umbral or the annularity path limits within a few meters. We discuss an experimental design with six observers. The comparison with other eclipses allows us to ascertain the solar variations. Measurements from the northern and the southern limits of the eclipse’s path give the polar solar diameter while observations near the center line give the equatorial diameter. The accuracy is good enough to detect a quadrupole momentum J2 ≥ 10-5.