UBVRI Photometry of SN 1993J in M81: Days 3 to 365

We present optical photometry of SN 1993J in M81 over the period 1993 March 30 to 1994 March 28, exactly one year after its discovery, recalibrating early data we had published in a previous paper and describing new data which cover the latter six months. At late times, the supernova's luminosity declined exponentially in BVRI, at a rate much faster than that of most Type II SNe. The rate of decline was smallest in R , probably due to the growth of strong [O I] and Hα emission lines. Measured 300 days into its evolution, SN 1993J was less luminous than other Type II SNe.