2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/6457We analyse late-time observations, available photometry and spectra, of a sample of type II plateau supernovae (SNe IIP). The possibility of using H$α$ luminosity at the nebular epoch as a tracer of $^{56}$Ni mass in this class of objects is investigated, yielding a consistency with the photometry-based estimates within 20%. Interesting correlations are found and their impacts on our present understanding of the physics of core collapse SNe are discussed.5 pages, 4 figures, Proceedings of IAU Colloquium 192, 'Supernovae (10 years of SN1993J)', 22-26 April 2003, Valencia, SpainAstrophysicstext