M31 is a very tempting target for a microlensing search of compact objects in
galactic haloes. It is the nearest large galaxy, it probably has its own dark
halo, and its tilted position with respect to the line of sight provides an
unmistakable signature of microlensing. However most stars of M31 are not
resolved and one has to use the ``pixel method'': monitor the pixels of the
image rather than the stars. AGAPE is the implementation of this idea. Data
have been collected and treated during two autumns of observation at the 2
metre telescope of Pic du Midi. The process of geometric and photometric
alignment, which must be performed before constructing pixel light curves, is
described. Seeing variations are minimised by working with large super-pixels
(2.1) compared with the average seeing. A high level of stability of pixel
fluxes, crucial to the approach, is reached. Fluctuations of super-pixels do
not exceed 1.7 times the photon noise which is 0.1% of the intensity for the
brightest ones. With such stable data, 10 microlensing events are expected for
a full ``standard halo''. With a larger field, a regular and short time
sampling and a long lever arm in time, the pixel method will be a very
efficient tool to explore the halo of M31.Comment: 15 pages, 15 figures. Text and figures with better definition will
also be available at http://cdfinfo.in2p3.fr/Experiences/AGAPE/publis.html
Modified according to the requirement of the referee. To appear in A&
