On even surfaces of general type with k^2=8, p_g=4, q=0

In this article we describe the moduli space of minimal surfaces of general type S with $K^2=8,p_{g}=4,q=0$, $K$ divisible by 2 and the canonical linear system $|K|$ base point free, showing that it forms an irreducible open set of the moduli space of minimal surfaces with $K^2=8,p_{g}=4,q=0$. By previous results of Ciliberto[Ci] and Ciliberto, Francia, Mendes Lopes [CFM], the above result shows that the moduli space of surfaces with $K^2=8,p_{g}=4,q=0$ has at least three connected components.