3 Conclusions

Observations of the solar diameter during 18 month from January 1997 to June 1998, to a total of 4630 single measurements were made at the ON. The error of a single observation is around 0$\hbox{$.\!\!^{\prime\prime}$}$6. Excepted some difference in the quality between the eastern and western measurements, no systematic effect is found, either from instrumental, weather or observational nature. In particular, the stability of the variable angle prism was confirmed. The daily measurements can therefore be grouped, resulting in 246 daily averages, to a precision better than 0$\hbox{$.\!\!^{\prime\prime}$}$2.

Further observations are highly desirable to improve the equipment performance and to study the solar semi-diameter variations in time. These are duly being conducted and currently a stepping up is planned for the dome of observation and for the instrument itself, along the lines of DORaySol (Delmas 1997).

Acknowledgements

This work was partially supported by the CNPq/CNRS, Brazil/ France binational agreement, under the number 910172/95-1. E.G.J. and S.P. thank CNPq for the financial support under the contracts 300016/93-0 and 300017/93-6.