All Figures

$\begin{figure} \par\includegraphics[width=18cm,clip]{Ms3987f11.eps} \end{figure}$ Figure 1: Left: General view of the modified Danjon astrolabe of Santiago. The telescope is a broken refractor of 10 cm aperture and 1 m focal distance. Right: The CERVIT reflecting prism and mercury mirror that define the fixed almucantar which is the benchmark for the solar drift. The prism angle is the only instrumental constant whose variation would affect the observational accuracy. Its stability during the solar drift (at most 7 min) is assured by the low thermal expansion coefficient of CERVIT. Reflected on the mercury can be seen a unit that contains the antenna and receiver of a GPS timer that provides Universal Time Coordinated (UTC) for accurate timing of the solar drift.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=17.8cm,clip]{Ms3987f21.ps} \end{figure}$ Figure 2: Solar radius measurements obtained with the astrolabe of Santiago at ${\rm 30^\circ }$ and ${\rm 60^\circ }$ zenith distances between May 1990 and April 2003. Each point represents a radius value deduced from a least squares solution of east and west observations of the solar borders made during the same day and reduced to the unit of distance (Noël 2003). ${\rm\sigma }$ is the average of the standard deviations given by the least square solutions and the figure in brackets is the number of radius measurements. From Santiago ( $\rm Lat.= \rm{-33\fdg4}$ ), the Sun is observable all year round at $60^\circ$ zenith distance and from October 6 until March 7 at $30^\circ$ .
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.8cm,clip]{Ms3987f31.ps} \end{figure}$ Figure 3: Monthly means of sunspot numbers given by SIDC and of solar radius measurements made with the Danjon astrolabe of Santiago. The smoothing curves are Vondrak's fits with the same smoothing parameter for sunspots and radius (Vondrak 1969). The monthly means of solar radius were computed combining the daily results at $30^\circ$ and $60^\circ$ zenith distances given in Fig. 2.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.8cm,clip]{Ms3987f41.ps} \end{figure}$ Figure 4: Linear correlations between monthly means of sunspot numbers and of apparent solar radius observed with the astrolabe of Santiago at ${\rm 60^\circ }$ and ${\rm 30^\circ }$ zenith distances (z). The higher correlation coefficient (r) given by the radius measurements at ${\rm 30^\circ }$ which are less affected by atmospheric noise, can be considered as an additional evidence that solar activity and radius variations would be causally related.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=18cm,clip]{Ms3987f51.ps} \end{figure}$ Figure 5: Variations of sunspot numbers and solar radius between 1982 and 2002. The sunspot numbers are monthly averages obtained from the home page of SIDC. The circles are annual deviations from the mean solar radius obtained with the solar magnetograph at Mount Wilson Observatory (1982-1994), with the visual astrolabe of Santiago (1991-2002) and with the CCD astrolabe of Rio de Janeiro (1997-2000). The diameters of the circles are of the order of the mean error of the annual values. The values for Mount Wilson were adapted from Fig. 1 of Ulrich & Bertello (1995). The pointed curve is a numerical fit applied to the individual radius measurements obtained by Laclare with the visual astrolabe of Calern. It was adapted from Fig. 1 of Delmas & Laclare (2002). The discrepancy between the visual astrolabes of Calern and Santiago is discussed in the text. The values of Rio de Janeiro were deduced from the radius measurements published by Jilinski et al. (1999), Puliaev et al. (2000) and Penna et al. (2002), after eliminating internal inconsistences of the original data (for details see Noël 2002).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.8cm,clip]{Ms3987f61.ps} \end{figure}$ Figure 6: Deviations from the mean of the solar radius according to its angle from the equator (heliographic inclination) as observed with the visual astrolabes of Calern and Santiago (Noël 1999). The smoothing curve is a Vondrak fit (Vondrak 1969) applied to the results of Santiago to reduce them to the values of heliographic inclination of Calern results (see Fig. 7).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.8cm,clip]{Ms3987f71.ps} \end{figure}$ Figure 7: Linear correlation with its correlation coefficient (r) between the results of Calern and Santiago given in Fig. 6. The results are those obtained from the common zone of the solar border observable from both sites (see text and Fig. 6).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=8.8cm,clip]{Ms3987f31.ps} \end{figure}$	Figure 3: Monthly means of sunspot numbers given by SIDC and of solar radius measurements made with the Danjon astrolabe of Santiago. The smoothing curves are Vondrak's fits with the same smoothing parameter for sunspots and radius (Vondrak 1969). The monthly means of solar radius were computed combining the daily results at $30^\circ$ and $60^\circ$ zenith distances given in Fig. 2.
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$\begin{figure} \par\includegraphics[angle=-90,width=8.8cm,clip]{Ms3987f61.ps} \end{figure}$	Figure 6: Deviations from the mean of the solar radius according to its angle from the equator (heliographic inclination) as observed with the visual astrolabes of Calern and Santiago (Noël 1999). The smoothing curve is a Vondrak fit (Vondrak 1969) applied to the results of Santiago to reduce them to the values of heliographic inclination of Calern results (see Fig. 7).
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$\begin{figure} \par\includegraphics[angle=-90,width=8.8cm,clip]{Ms3987f71.ps} \end{figure}$	Figure 7: Linear correlation with its correlation coefficient (r) between the results of Calern and Santiago given in Fig. 6. The results are those obtained from the common zone of the solar border observable from both sites (see text and Fig. 6).
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