A hemispherical detector comprising a plurality of photodetectors arranged in a substantially contiguous array, the array being substantially in the shape of a half-sphere, the half-sphere defining a closed end and an open end, the open end defining a substantially circular face. Also provided is a method for constructing a hemispherical detector comprising the steps of making a press mold of the desired shape of the hemispherical detector, pouring a material into the press mold to form a cast, finishing the cast to remove any defects, coating the cast with a coating material, and attaching a plurality of photodetectors to the cast.