MAXGridspacing d :

This keyword determines the extend (highest resolution) of the transform. It corresponds to the maximum acceptable (by the user) separation (in Å) between successive grid points on any of the directions of the cell that will be used for calculating the molecular transform. The value of d should be at least one-third of the maximum resolution of the data that you intend to use. In addition, you should not use too coarse a grid because serious errors will be introduced during the calculation of the electron density map. Values of d of the order of up to 1.0Å are possibly OK.