[phenixbb] MRC map as molecular replacement model

Hi all, I want to use an MRC map obtained by low resolution EM reconstruction, as molecular replacement model in Phaser. I serached the phenixbb archives and learned that I should us phenix.map_to_structure_factors to convert the map file to mtz so it can be input into Phaser. When I do that I get an error "Sorry: Map must have origin at (0,0,0): recenter the map and try again". I have two questions? 1) What tool should I use to recenter the map and 2) Is there a better way to do this? Thanks in advance for your replies. Best regards, Priyamvada