We describe an XMM-Newton observation of the PKS0312-770 field , which facilitates the spectral analysis of serendipitous sources previously detected by CHANDRA .
The combination of larger effective area and longer exposure duration allows a significant increase in detected photons , and a lower limit in source detection sensitivity .
In particular the hard X-ray normal galaxy unveiled by Fiore et al ( 2000 ) is most likely explained as a moderately absorbed ( N _ { H } \sim 10 ^ { 22 } cm ^ { -2 } ) AGN .
We detect 52 sources ( 45 previously unreported ) at a limiting flux of \sim 2 10 ^ { -15 } ergs cm ^ { -2 } s ^ { -1 } in the 0.5-2keV band .
The LogN-LogS curve is consistent with that derived from by XMM-Newton observations of the Lockman Hole field .
The flux determinations allow to check for any inconsistency between the calibrations of the two observatories , which is discussed .