  We have studied the stellar main sequence (MS) of the globular cluster
NGC2298 using deep HST/ACS observations in the F606W and F814W bands covering
an area of 3.4' x 3.4' around the cluster centre or about twice the cluster's
half-mass radius. The colour-magnitude diagram that we derive in this way
reveals a narrow and well defined MS extending down to the 10 sigma detection
limit at m_606~26.5, m_814~25, corresponding to stars of ~0.2 Msolar. The
luminosity function (LF) obtained with these data, once corrected for the
limited effects of photometric incompleteness, reveals a remarkable deficiency
of low-mass stars as well as a radial gradient, in that the LF becomes
progressively steeper with radius. Using the mass-luminosity relation
appropriate for the metallicity of NGC2298, we derive the cluster's global mass
function (GMF) by using a multi-mass Michie-King model. Over the range 0.8 -
0.2 Msolar, the number of stars per unit mass decreases following a power-law
distribution of the type dN/dm \propto m^(0.5), where, for comparison, typical
halo clusters have dN/dm \propto m^(-1.5). If the IMF of NGC2298 was similar to
that of other metal poor halo clusters, like e.g. NGC6397, the present GMF that
we obtain implies that this object must have lost of order 85% of its original
mass, at a rate much higher than that suggested by current models based on the
available cluster orbit. The latter may, therefore, need revision.
