2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/10029A photoelectric monitoring program has been applied, during the last four years, to five central stars of planetary nebulae (PNNs) with strong O\,VI $λ$ 3811--34 Å\hspace{0.1mm} emission. NGC\,6905 and, marginally, NGC\,2452, show intrinsic luminosity variations, while NGC\,7026, IC\,2003 and NGC\,1501 have constant luminosity within a few mmag. Photometric data have been analyzed with the best available packages for power--spectra reductions. Both pulsators have periods and physical characteristics well encompassed by the theoretical pulsational models relative to these stars.6 pages, uuencoded file (figures included), accepted by Astronomy and Astrophysics, May 1995Astrophysicstext