GHASP:: An Hα kinematic survey of spiral and irregular galaxies -: I.: Velocity fields and rotation curves of 23 galaxies

GHASP (Gassendi Halpha survey of SPirals) is a survey of Halpha velocities in spiral and irregular galaxies. The observations began in 1998, with a scanning Fabry-Perot and a focal reducer attached at the Cassegrain focus of the 1.93 m telescope at the Observatoire de Haute-Provence. This paper presents the Halpha maps, the 2D velocity fields and the rotation curves obtained for a set of 23 galaxies observed in October 1998 and April 1999. Most of them have already been observed in HI in the frame of the WHISP survey led at Westerbork, for which GHASP brings an interesting complement. The aim is to provide a reference sample of 2D velocity fields for about 200 nearby spiral galaxies at Halpha wavelength.