On-sky observations with an achromatic hybrid phase knife coronagraph in the visible L. Abe, M. Beaulieu, F. Vakili, J. Gay, J.-P. Rivet, S. Dervaux and A. Domiciano de Souza A&A, 461 1 (2007) 365-371 Published online: 04 October 2006 DOI: 10.1051/0004-6361:20065150