A series expansion of Conwayʹs generalised solid-angle formulas

A series expansion is presented of Conwayʹs solid-angle formula for two parallel, non-coaxial discs. Similar equations for non-coaxial, parallel ring and point sources are verified, as well as a quickly converging integral representation for the solid angle of two coaxial discs. Their performance is tested by comparison with results from a numerical integration method.