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Astron. Astrophys. 325, 825-827

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Variations of the apparent solar semidiameter observed
with the astrolabe of Santiago

F. Noël

Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile

Received 27 February 1997 / Accepted 11 April 1997


Measurements of the Sun semidiameter made with the Danjon astrolabe at Santiago, Chile, and with the magnetograph of the solar telescope of Mount Wilson Observatory during the period 1990-1995, show similar variations in time and with a similar trend as the variation of sunspot number. The consistency of these results obtained at different sites and with rather different observing techniques could be considered as an empirical evidency that a causal connection may exist between the solar activity and the variations of the apparent solar radius as observed at Santiago and Mount Wilson.

Key words: astrometry - Sun: fundamental parameters - methods: observational

Send offprint requests to: F. Noël

© European Southern Observatory (ESO) 1997

Online publication: September 9, 1997
Last change: April 28, 1998