heliograph

Concise Oxford English Dictionary © 2008 Oxford University Press:
heliograph/ˈhiːliəɡrɑːf/

▶noun

• 1 a signalling device by which sunlight is reflected in flashes from a movable mirror.

  ■ a heliogram.

• 2 a telescopic apparatus for photographing the sun.

• 3 a type of early photographic engraving made using a sensitized silver plate and an asphalt or bitumen varnish.

▶verb

• 1 send (a message) by heliograph.

• 2 take a heliographic photograph of.

– derivatives
heliographic adjective,
heliography noun.