  We present new estimates of the observed rates of SNe determined with the
{\em control time} method applied to the files of observations of two long
term, photographic SN searches carried out at the Asiago and Sternberg
Observatories. Our calculations are applied to a galaxy sample extracted from
RC3, in which 65 SNe have been discovered. This relatively large number of SNe
has been redistributed in the different morphological classes of host galaxies
giving the respective SN rates. The magnitude of two biases, the overexposure
of the central part of galaxies and the inclination of the spiral parent
galaxies, have been estimated. We show that due to overexposure a increasing
fraction of SNe is lost in galaxies of increasing distances. Also, a reduced
number of SNe is discovered in inclined galaxies ($i>30\degr$): SNII and Ib are
more affected than Ia, as well as SNe in Sbc-Sd galaxies with respect to other
spirals. We strengthen previous findings that the SN rates is proportional to
the galaxy blue luminosity for all SN and Hubble types. Other sources of
errors, besides those due to the statistics of the events, have been
investigated. In particular those related to the adopted SN parameters
(Cappellaro et al. (\cite{paper1})) and correction factor for overexposure and
inclination. Moreover, we show that the frequencies of SNe per unit luminosity
vary if different sources for the parameters of the sample galaxies are
adopted, thus hampering the comparison of SN rates based on different galaxy
samples. The overall rates per unit blue luminosity are similar to the previous
