The quasi-simultaneous measurement of the one-dimensional angular separation of stars on the sky, on both small and large angular scales, rely on the measurements made by the IDT detector, as well as on inputs from the star mapper and attitude control system. This presentation will concentrate on the results of a comparison of the results of the IDT data processing carried out by the FAST and NDAC data analysis teams. The extent to which the intensity and phase measurements agree between the two reductions, and the extent to which the differences are consistent with expected photon noise errors, will be illustrated.