SS Cygni - A new period and discussion of orbital parameters

New spectroscopic observations of the dwarf Nova SS Cygni show the accepted orbital period to be substantially in error so that the phases computed from the published ephemeris cannot be used. A revised period and velocity amplitude for each star lead to new estimates of the component masses. However, systematic differences exist in velocities from different data sets, which appear to be real. The new ephemeris is essential for the understanding of the phase correlation of recent X-ray and UV data. Through examination of the emission-line profiles and other quantities, limits are set on the orbital inclination.