Planck CollaborationAde, P. A. R.P. A. R.AdeAghanim, N.N.AghanimNatoli, PaoloPaoloNatoliPolenta, GianlucaGianlucaPolenta2020-09-172020-09-172015-04-01https://hdl.handle.net/20.500.13025/4392eprint arXiv 1504.04583We present the results of approximately three years of observations of Planck Sunyaev-Zeldovich (SZ) sources with telescopes at the Canary Islands observatories, as part of the general optical follow-up programme undertaken by the Planck collaboration. In total, 78 SZ sources are discussed. Deep imaging observations were obtained for most of those sources; spectroscopic observations in either in long-slit or multi-object modes were obtained for many. We found optical counterparts for 73 of the 78 candidates. This sample includes 53 spectroscopic redshifts determinations, 20 of them obtained with a multi-object spectroscopic mode. The sample contains new redshifts for 27 Planck clusters that were not included in the first Planck SZ source catalogue (PSZ1).Astrophysics - Cosmology and Nongalactic Astrophysics Comment 15 pages14 figuressubmitted to A&Ahttp://adsabs.harvard.edu/abs/2015arXiv150404583P2015arXiv150404583P