A gamma-ray detector for determining the direction to a source of gamma-rays is described. The detector comprises a first scintillation body coupled to a first photodetector and a second scintillation body coupled to a second photodetector, wherein the first scintillation body and the second scintillation body are arranged to be co-axial with a pointing axis of the detector. The detector further comprises a processing circuit arranged to receive output signals associated with the first and second photodetectors for a plurality of different orientations of the pointing axis of the detector relative to a reference direction. The processing circuit is further operable to determine a direction to the source of gamma-rays relative to the reference direction based on output signals associated with the first and second photodetectors for the plurality of different orientations of the pointing axis of the detector relative to the reference direction.