This procedure is used to fit pairs to individual nights. The list of nights is derived from the ones currently loaded, and they are re-loaded (load_interferometry) despite the overhead in order to allow data sets of the same night to be combined. Initial estimates for are obtained from the orbital elements. The results are written to file fitnights.psn, including fitted synthesized beam widths. This file is in the standard astrometry format and can be read back into AMOEBA.