ABSOLUTE FLUXES FOR SUPERNOVA 1987A .3. DAYS 158-314

We present the third part of our atlas of high-precision flux-calibrat ed optical spectrophotometry of SN 1987A obtained at the 0.61 m Bochum telescope. Here we cover days 158-314. The evolution of the spectra d uring the transition of the supernova from the stellar to the nebular phase is described. We give line luminosities, equivalent widths and r adial velocities for the most important lines. Finally, we investigate the stratification of the expanding envelope.