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 \pm 0.02 { 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 _ { 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 Å 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 .