EMISSION-LINE IMAGING OF 3CR RADIO GALAXIES .1. IMAGING DATA

We present emission-line and continuum images of a sample of 53 3CR ra dio galaxies with 0.05 < z < 2.0. Each object was imaged in one of the following emission lines: H alpha, [O III] lambda 5007, [O II] lambda 3727, or Ly alpha. The visible continuum, emission-line, and radio mo rphologies of each object are described. The galaxies show a wide rang e of structures on scales ranging from subkiloparsec circumnuclear emi ssion-line regions to 300 kpc nebulae. For z > 0.3 nearly all of the e mission-line regions are aligned with their radio source axes. At reds hifts greater than similar to 0.6 the optical/UV continua show a stron g alignment with the radio axes. All of the emission-line regions show a strong correlation with the arm-length asymmetry of their radio sou rce. The data presented here are analyzed in Paper II.