A&A Supplement series, Vol. 123, June I 1997, 403-410
Received June 12; accepted September 25, 1996
J.L. Penna
- P. Benevides-Soares
- A.H.
Andrei
- F. Laclare
Send offprint request: J.L. Penna,Observatorio Nacional/CNPq, R. Gal. José
Cristino 77, CEP 20921-400, Rio de Janeiro, e-mail: jucira@on.br
Observatorio Nacional/CNPq, Brasil
Instituto Astronômico e Geofísico/USP, Brasil
Observatoire de Calern/OCA, France
In this work we investigate
on the stability of the results from solar observations obtained
with the modified astrolabes of the Observatoire de la Côte
d'Azur/France, of the Observatório Abrahão de
Moraes/IAG/USP-Brazil and of the Observatório
Nacional/Brazil. The mass of data is comprised of 6273
observations of both solar limbs, from 1974 to 1992, and is
analyzed to determine the origin of the fundamental reference
system and the Earth's orbital parameters.
The solution stability was verified by checking against any large variation
upon the individual weights, as well as for different sub samples
of the whole set of observations. The results were also shown
invariant to changes in the adopted model, such as adding unknowns
to the refraction algorithm, to the time variation of the obliquity
(including the nutation constant) and to the azimuthal anomalies of
the refraction.
In our analysis we obtain a standard deviation of 
for the
combination of the observations with no bias on its distribution. It is
also indicated that the Sun observations at astrolabes do not require any
further atmosphere modelling complexity.
keywords: astrometry -- reference system -- Sun: general -- methods: data analysis