1. A method of registering a first camera to a second camera of a multi-camera imager (MCI), each camera modeled as a pin hole camera having a center of projection, an optical axis extending from the center of projection, a camera coordinate system having an origin at the center of projection and a Z axis coincident with the optical axis, an image plane intersected by the optical axis at a principal point, and a photosensor comprising pixels on which the camera images scenes, the method comprising: operating the first and second cameras to acquire first and second images respectively of a calibration target located at a known position relative to the MCI and comprising fiducials that define at least two lines in the calibration target; determining at least one angle between two lines defined by images of the fiducials in a projection of the image of the calibration target acquired by at least one of the first and second cameras on the image plane of the camera; and using the at least one angle to register the first and second cameras to each other.