A first principles approach is presented for calculations of optical -- ultraviolet (UV) spectra including excitonic effects. The approach is based on Bethe-Salpeter equation calculations using the textsc{NBSE} code combined with ground-state density
-functional theory calculations from the electronic structure code textsc{ABINIT}. Test calculations for bulk Si are presented, and the approach is illustrated with calculations of the optical spectra and birefringence of $alpha$-phase SiO$_2$ and the rutile and anatase phases of TiO$_2$. An interpretation of the strong birefringence in TiO$_2$ is presented.
