Red parts of the SDSS spectra of three selected program stars (lower spectra). The upper SDSS spectrum is from a known PG 1159 star (PG 1144+005). The O vi emission feature at 7870 Å in the models is possibly related to the unidentified emission feature at 7717 Å. Each spectrum is labeled with T_eff , log g, C/He number ratio of the overplotted model. If applicable, other element abundances in the models are indicated, too.