Astron. Astrophys. Suppl. Ser. 137, 269-272

Absolute declinations with the photoelectric astrolabe at Calern Observatory (OCA)

V.A.F. Martin ^1,2, N.V. Leister ³, G. Vigouroux ⁴, M. Furia ⁴, - A. Journet ⁴

Send offprint request: V.A.F. Martin,
e-mail: vmartin@uefs.br

1 - Observatório Astronômico Antares, Universidade Estadual de Feira de Santana, Rua da Barra, 925, cep: 44015-430, Feira de Santana, Bahia, Brazil
2 - Departamento de Física, Universidade Estadual de Feira de Santana, Rodovia BR116 Norte, km 03, Campus Universitário, cep: 44031-460, Feira de Santana, Bahia, Brazil
3 - Instituto Astronômico e Geofísico, Universidade de São Paulo, Av. Miguel Stéfano, 4200, cep: 04301-970, São Paulo SP, Brazil
4 - Observatoire de la Côte d'Azur, C.E.R.G.A., avenue Copernic, F-06130 Grasse, France

Received September 22; accepted March 18, 1999

Abstract:

A regular observational programme with a photoelectric astrolabe have been performed at "Observatoire du Calern" (Observatoire de la Côte d'Azur, OCA, $\phi$ = $+43^{\rm o}44{\hbox{$^\prime$}}55.011{\hbox{$^{\prime\prime}$}}$; $\lambda$ = $-0^{\rm h}27^{\rm m}42.44^{\rm s}$, Calern, Caussols, France) for the last twenty years. It has been almost fully automatized between 1984 and 1987. Since 1988 the photoelectric astrolabe was used without any modification. In addition to determining the daily orientation of the local vertical, the yearly analysis of the residuals permits to derive corrections to the used star catalogue (Vigouroux et al. 1992).

A global reduction method was applied for the ASPHO observations. The new form of the equations (Martin & Leister 1997) give us the possibility of using the entire set of the observing program using data taken at two zenith distances ($30^{\rm o}$ and $45^{\rm o}$).

The program contains about 41648 stars' transits of 269 different stars taken at "Observatoire du Calern" (OCA).

The reduction was based on the HIPPARCOS system. We discuss the possibility of computing absolute declinations through stars belonging simultaneously to the $30^{\rm o}$ and $45^{\rm o}$ zenith distances programmes. The absolute declination corrections were determined for 185 stars with precision of 0.027$\hbox{$^{\prime\prime}$}$ and the value of the determined equator correction is -0.018$\hbox{$^{\prime\prime}$}$ $\pm$ 0.005$\hbox{$^{\prime\prime}$}$. The instrumental effects were also determined. The mean epoch is 1995.29.

Key words: astrometry -- catalogues -- reference system