We study the propagation of cosmic rays at the highest energies of different compositions and discuss the implications for anisotropy studies of future UHECR observatories. The evolution of the horizon of cosmic rays as a function of the energy is mass dependent: low and intermediate mass nuclei can only originate from very nearby sources above a few 10^19 eV and the composition above 4.10^19 eV should be mainly protons with a small iron fraction. We show the expected sky anisotropies between 10^19 and 10^20.5 eV for exposures from 10^4 to 10^6 km^2 sr yr.

Proceedings of the 30th International Cosmic Ray Conference; Rogelio Caballero, Juan Carlos D'Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia (eds.); Universidad Nacional Autónoma de México, Mexico City, Mexico, 2008; Vol. 4 (HE part 1), pages 527-530