WeCAPP: Wendelstein Calar Alto Pixellensing Project: Capturing dark matter in M31

I present (WeCAPP) our long time project searching for microlensing events in M31. Since 1997 the bulge of M31 was monitored in two different wavebands with the Wendelstein 0.8 m telescope. In 1999 we extended our observations to the Calar Alto 1.23m telescope. Observing simultaneously on these two sites we obtained a larger than 60% time coverage of the visibility of M31. To check thousands of frames for variability of unresolved sources, we used the image subtraction method proposed by Alard & Lupton (1998). With this method we were able to minimize the residuals in the difference image analysis (Tomaney & Crotts 1996) and to detect sources with an amplitude near the photon noise level. With the expected microlensing events and their timescales, it will be possible to favour or rule out a certain MACHO population and to derive constraints for the dark matter compound of M31.