| Abstract | dc.description.abstract | Ground-based results on cyclic variations of the apparent solar radius are so far controversial
and inconsistent. This is blamed to atmospheric noise which effects can be so severe that
even in cases in which the observations are made with similar instruments, the results show strong
disagreements (Li et al.: 2003, Astrophys. J. 591, 1267). Such claim concerns the results of Danjon
astrolabes which during the last decades have been used widely at several sites for solar metrology.
The long-term series with thousands of radius measurements made with astrolabe at Calern, France,
and at Santiago, Chile, is a case in which the results of radius variations in time are strongly discrepant
in spite that the observations were made simultaneously, in quite similar conditions and with
almost identical instruments (No¨el: 2004, Astron. Astrophys. 413, 725). However, we show here that
most of astrolabe discrepancies may be due to data analysis biased by theoretical preconceptions, by
empirical results which without scientific arguments are considered as canonical references and by
over interpretations of casual agreements between visual and CCD astrolabe results. | en |
