1 Introduction

The aim of this work is to determine proper motions and parallaxes of open clusters using the Hipparcos Catalogue (ESA 1997). We will focus here on the more distant open clusters and try to find proper motions for all clusters with distances greater then D=200 pc. In combination with accurate photometric distances and radial velocities, the proper motions will provide valuable information on the kinematic parameters of the galactic rotation curve and the distance to the galactic centre. They are also useful to study the formation and evolution of the open cluster system. These questions will be addressed in a forthcoming paper. The present paper provides the observational database for these studies.

Stars in open clusters were searched and proposed by Wielen & Dettbarn (1985) and selected by a specific working group within the INCA Consortium during the creation of the Hipparcos Input Catalogue. However, the Hipparcos Catalogue may contain additional cluster stars not selected by this working group: first, there may exist bright cluster stars that have so far not been studied at all or were studied in detail only after the creation of the Hipparcos Input Catalogue. Such stars could have entered the Hipparcos Catalogue as part of the all sky survey. In addition, cluster stars may have been proposed by other research groups if they are of astrophysical interest.

It therefore seemed appropriate to perform a new search for stars in open clusters. Sections 2 and 3 describe the selection of the open clusters and the search for Hipparcos stars in the cluster fields.

Section 4 describes the way in which cluster members were identified among the candidates and the next section describes how the mean astrometric parameters of the clusters were determined. Section 6 lists the classification of the Hipparcos stars and presents the mean astrometric parameters of the open clusters. Two applications of the astrometric parameters are also described in this section. First, we compare the Hipparcos parallaxes with the photometric parallaxes of the open clusters to check for systematic errors in both methods. Second we use the proper motions of the open clusters to check the membership of several Cepheids. Section 7 summarises our results.