  In a Brans-Dicke (BD) cosmological model, the energy density associated with
some scalar field decreases as $\displaystyle a^{{-2}(\frac{\omega_{o}+
{\frac12}%}{\omega_{o}+1})} $ with the scale factor $a(t)$ of the Universe,
giving a matter with an Equation of state $\displaystyle
p=-{1/3}(\frac{2+\omega_{o}}{1+\omega_{o}}) \rho $. In this model, the Universe
could be closed but still have a nonrelativistic-matter density corresponding
to its critical value, $\Omega_{o}=1$. Different cosmological expressions, such
as, luminosity distance, angular diameter, number count and ratio of the
redshift tickness-angular size, are determined in terms of the redshift for
this model.
