Since the first neutron diffraction studies of manganese and nickel monoxides  the interest to the magnetic and crystal structures of MnO and NiO is kept up, see e.g. experimental study  and theoretical first principal calculations  and references cited therein. It is well established experimentally that below N ́eel temperature the crystal structure is metrically lowered in symmetry from cubic Fm̄3m to rhombohedral R̄3m, or might be to monoclinic one. However, the allowed by symmetry monoclinic distortions from rhombohedral R̄3m-metric are very small and the explicit monoclinic splittings of the diffraction peaks have not been experimentally observed. We analyse in full details all possible magnetic crystallographic models metrically compatible with the experiment by using isotropy subgroup representation approach based on the propagation vector star. The models (some not previously considered) are compared with the high resolution and high intensity diffraction data measured at the HRPT diffractometer at Swiss neutron spallation source SINQ.