  We present optical photometry and spectroscopy of the type IIP supernova SN
2004et that occurred in the nearby galaxy NGC 6946. The observations span a
time range of 8 days to 541 days after explosion. The late time bolometric
luminosity and the H$\alpha$ luminosity in the nebular phase indicate that
$0.06\pm0.02{M_\odot}$ of $^{56}$Ni was synthesised during the explosion. The
plateau luminosity, its duration and the expansion velocity of the supernova at
the middle of the plateau indicate an explosion energy of $E_{\rm{exp}}=
1.20^{+0.38}_{-0.30} \times 10^{51}$ ergs. The late time light curve and the
evolution of the [OI] and H$\alpha$ emission line profiles indicate the
possibility of an early dust formation in the supernova ejecta.
  The luminosity of [OI] 6300, 6364 \AA doublet, before the dust formation
phase, is found to be comparable to that of SN 1987A at similar epochs, impling
an oxygen mass in the range $1.5 - 2{M_\odot}$, and a main sequence mass of
$20{M_\odot}$ for the progenitor.
