  The convolution sum, $\underset{\substack{ {(l,m)\in\mathbb{N}_{0}^{2}}
{\alpha\,l+\beta\,m=n} } }{\sum}\sigma(l)\sigma(m)$, where $\alpha\beta=44,52$,
is evaluated for all natural numbers $n$. We then use these convolution sums to
determine formulae for the number of representations of a natural number by the
octonary quadratic forms $a\,(x_{1}^{2} + x_{2}^{2} + x_{3}^{2} + x_{4}^{2})+
b\,(x_{5}^{2} + x_{6}^{2} + x_{7}^{2} + x_{8}^{2})$, where $(a,b)=
(1,11),(1,13)$.
