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3 Reductions and results

All the observations were reduced using the DE200/LE200 ephemeris of the Sun. The orientation of the local reference frame is obtained by means of the Earth rotation parameters (polar coordinates and UT1-UTC) interpolated from Bulletins B published by the Central Bureau of the International Earth Rotation Service (IERS). A detailed description of the reduction method applied at Santiago for solar observations was given by Chollet & Noël (1993).

The average annual values of the differences in right ascension (astrolabe-ephemeris) and those of the observed Sun semidiameter reduced to the astronomical unit, obtained during the period 1995-1997 and during former years of the solar program are given in Table 1.

 
Table 1: Yearly mean values in right ascension (observed-ephemeris) and solar semidiameter, and their mean errors, derived from astrolabe observations of the Sun. n is the number of individual measurements involved

\begin{tabular}
{llll}
\hline\noalign{\smallskip}
Year & \ \ Alpha (O$-$E) & Sem...
 ...\:\: 0.03$\space & \ \ \ \ \ \ \ 120 \\ \noalign{\smallskip}
\hline\end{tabular}

The individuals results of the observations at $30\hbox{$^\circ$}$ and $60\hbox{$^\circ$}$ for the period 1995-1997 are reported in Tables 2 and 3 respectively (accesible only in electronic form) with results of former observational periods. The following information is available from these tables:


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