heliograph

From helio- +‎ -graph.

heliograph (plural heliographs)

1. An apparatus for signalling by means of a moveable mirror which reflects flashes of sunlight.
   • 1979, Alasdair Gray, ‘Five Letters From an Eastern Empire’, Canongate 2012 (Every Short Story 1951-2012), p. 93:

     when we stood up at nightfall we saw, in the sunset, the sparkle of the heliograph above cities, on the far side of the horizon.

2. A heliogram.
3. An instrument for measuring the intensity of sunlight.
4. A device for photographing the sun.
5. (obsolete) A photograph.

heliograph (third-person singular simple present heliographs, present participle heliographing, simple past and past participle heliographed)

1. (transitive) To send a message by heliograph.
2. (intransitive) To send a heliograph.
3. (transitive, dated) To photograph by sunlight.

• heliographer
• heliographic
• heliography