actinograph
/akˈtɪnəɡrɑːf/ /akˈtɪnəɡraf/noun
1An instrument for recording variations in the intensity of solar radiation.
2 Photography. A form of calculator for estimating the actinic power of daylight, to aid in determining an appropriate exposure. Now historical.
Origin
Mid 19th century; earliest use found in John Herschel (1792–1871), mathematician and astronomer. From actino- + -graph.