arXiv:0804.1795v1 [astro-ph] 10 Apr 2008 Accepted for publication in AJ A large-scale optical-near infrared survey for brown dwarfs and very low-mass stars in the Orion OB1 association Juan Jos´e Downes W. Centro de Investigaciones de Astronom´ıa, Apartado Postal. 264, M´erida 5101-A, Venezuela Escuela de F´ısica, Universidad Central de Venezuela, Apartado Postal 47586, Caracas 1041-A, Venezuela jdownes@cida.ve C´esar Brice˜ no Centro de Investigaciones de Astronom´ıa, Apartado Postal. 264, M´erida 5101-A, Venezuela briceno@cida.ve Jes´ us Hern´andez Department of Astronomy, University of Michigan, 825 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 Centro de Investigaciones de Astronom´ıa, Apartado Postal. 264, M´erida 5101-A, Venezuela hernandj@umich.edu Nuria Calvet & Lee Hartmann Department of Astronomy, University of Michigan, 825 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 ncalvet@umich.edu, lhartm@umich.edu Ernesto Ponsot Balaguer Facultad de Ciencias Econ´omicas y Sociales, Universidad de los Andes, M´erida, 5101, Venezuela ernesto@ula.ve