An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

1) An instrument for photographing the Sun, consisting of a camera and a specially adapted telescope.
2) A simple device using a mirror to reflect sunlight to a distant observer. By moving the mirror, flashes of light can be used to send coded messages. The heliograph was a highly effective instrument for instantaneous optical communication over 80km or more in the 19th century.
3) Meteo.: An instrument which records the duration of sunshine and gives a quantitative measure of the amount of sunshine.

→ helio-; + → -graph.

An instrument for recording monochromatic images of the Sun.

→ spectro-; → heliograph.