actinographn.

1840 J. F. W. Herschel in Philos. Trans. (Royal Soc.) 130 46 (heading) Description of an actinograph, or self-registering photometer for meteorological purposes.

1853 R. Hunt Man. Photogr. (ed. 3) 154 The instrument constructed by Sir John Herschel, which he has named an actinograph, not only registers the direct effect of solar chemical radiation, but also the amount of general actinic power in the visible hemisphere.

1926 Ecology 7 332 Various photometers and actinographs are manufactured for this purpose [sc. showing the intensity of indirect sunlight].

2004 T. Muneer in T. Muneer Solar Radiation & Daylight Models (ed. 2) i. 27 The author has..visited a solar radiation measurement station in the middle of the Sahara desert and seen the Robitzch actinograph faithfully recording a regular trace of irradiation.

1890 Internat. Ann. Anthonys Photogr. Bull. 432 The actinograph [before us] is..an ingenious application of the slide rule for the purpose of determining photographic exposures.

1902 Encycl. Brit. XXX. 702/1 In Hurter & Driffield's ‘Actinograph’, the light coefficient is given by a printed card showing the curves for every day in the year.

2003 B. J. Suess Creative Black & White Photogr. (rev. ed.) iii. 15 The actinograph was a series of revolving scales used to calculate the intensity of light according to the day of the year and ‘the state of the atmosphere’.