Absolute declinations from astrolabe data

¹ Instituto Astronômico e Geofísico, Universidade de São Paulo, CP 9638, 01065-970 São Paulo, SP, Brazil
² Observatoire de la Côte d'Azur/C.E.R.G.A., Avenue Copernic, F-06130 Grasse, France

Send offprint request to: V.A.F. Martin

Received: 24 September 1996
Accepted: 3 January 1997

Abstract

We show the results of an evaluation of a global reduction method for Danjon astrolabe observations. The approach is much simpler but more precise than the conventional method. The new form of the equations gives us the possibility of using the entire set of an observational programme using the data from different catalogues taken at two zenith distances ( and ). The observational programme contains about 15000 observations of 381 different stars taken at the "Observatório Abrahão de Moraes" (OAM, ϕ = 0006S; λ = W), Valinhos, São Paulo, Brazil. The reduction was based on the FK5 system. We discuss the possibility to compute absolute declinations through the stars belonging simultaneously to the and zenith distance programmes. The absolute declination corrections were determined for 269 stars with a precision of 0.13, and the value of the determined equator correction is 0.028 ± 0.034. The instrumental effects were also determined.