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We analyze $\sim$32 years of optical spectra and photometry for the symbioticbinary PU Vul. Light curves for the He I $\lambda$4471, He II $\lambda$4686 andH$\beta$ $\lambda$4861 emission lines reveal an illumination effect, where thehot white dwarf ionizes the outflowing wind of the red giant, and evidence foran eccentric orbit with e $\approx$ 0.16. Along with the gradual appearance ofhigh ionization emission from [Fe VII] and O VI, the relative fluxes of theselines suggest an increase in the effective temperature of the hot component,from roughly $10^5$ K on JD 2448000 (1990) to roughly $2\times 10^5$ K on JD2455000 (2009). During this period, the luminosity of the hot component droppedby a factor of 4$-$6 to a current value of roughly 1000 L$_{\odot}$.

An illumination effect and an eccentric orbit for the symbiotic binary PU Vul revealed by 32 years of optical spectroscopy