Hibon, P.Hammersley, P.Selman, F.Hau, G.Duhoux, P.Agnello, A.Arranda, I.Arsenault, R.Blanchard, I.Cerda, S.Egner, S.Johnston, E.Parraguez, D.Reyes, C.Vernet, E.2026-01-012026-01-01ORCID:/0000-0001-9632-2706/work/181568973https://hdl.handle.net/1885/733802043During the 2nd semester of 2016, a new Deformable Secondary Mirror (DSM), part of the Adaptive Optics Facility Project at Paranal Observatory, was installed on the Unit Telescope 4. Starting end of November 2016, we then re-commissioned the telescope and the following three instruments : HAWK-I, MUSE and SINFONI. It is important to understand how a DSM, even if used in non-adaptive optics mode (i.e., in its rest/at position), can impact the operations and the quality of the observations. We discuss here the results of this telescope and instrument re-commissioning, the challenges and problems we met, and compare the new performance to the ones obtained previously with the traditional Dornier Secondary Mirror.enPublisher Copyright: © 2017 Associazione Italiana di Metallurgia. All rights reserved.Adaptive opticsCommissioningDeformable mirrorVLT201710.26698/ao4elt5.012085049236166