A census of AGB stars in Local Group galaxies I. Photometry of a field in M 31

We present four colour CCD photometry of a field in M 31. Observations were carried out in two broad band filters (V and i) and two special narrow band "Wing" filters centered on a TiO and a CN molecular band. Colour-magnitude diagrams constructed from broad band photometry show the sequence of RGB/BGB stars. Three known Cepheid variables could be identified on our frames. We used colour-colour diagrams to identify the M- and C-type AGB stars and to investigate e.g. the luminosity function of the AGB population. We found 61 new extragalactic C-stars in this field of M 31.