Development of a passive visible spectroscopic diagnostic on HL-2A tokamak

•A passive visible spectroscopic diagnostic is first installed on HL-2A tokamak.•This diagnostic measure the profiles of line emission and continuum radiation simultaneously.•The absolute intensity calibration has been provided for this diagnostic.•The plasma-wall interaction and the subsequent effect on the Zeff is demonstrated by this diagnostic.•The line-integrated electron density profiles are measured by the visible bremsstrahlung for the first time on HL-2A.