A spectral analyzer and direction indicator is disclosed and is responsive to collimated or essentially collimated incident radiation. The spectral analyzer and direction indicator includes optical apparatus (13, 15, 113) for providing optical information including diffracted optical information. A detector structure (21, 23, 117) is responsive to the optical information to provide detection output information indicative of incidence direction and spectral content collimated or essentially collimated incident radiation. A processor (20, 120) determines whether the diffraction information includes second order diffraction.