ac·ti·nom·e·ter 
(ăk′tə-nŏmĭ-tər)
(ăk′tə-nŏmĭ-tər)n.
Any of several radiometric instruments, such as a pyrheliometer, used chiefly for meteorological measurements of terrestrial and solar radiation.
ac′ti·no·metric (-nō-mĕtrĭk), ac′ti·no·metri·cal adj.
ac′ti·nome·try n.