n. [ Helio- + -graph. ] [ 1913 Webster ]

1. A picture taken by heliography; a photograph. [ 1913 Webster ]

2. An instrument for taking photographs of the sun. [ 1913 Webster ]

3. An apparatus for telegraphing by means of the sun's rays. See Heliotrope, 3. [ 1913 Webster ]

v. t. 1. To telegraph, or signal, with a heliograph. [ Webster 1913 Suppl. ]

2. To photograph by sunlight. [ Webster 1913 Suppl. ]

a. (Astron.) 1. Of or pertaining to a description of the sun. [ Webster 1913 Suppl. ]

☞ Heliographic longitudes and latitudes of spots on the sun's surface are analogous to geographic longitudes and latitudes of places on the earth. [ Webster 1913 Suppl. ]

2. Of or pertaining to heliography or a heliograph; made by heliography. [ 1913 Webster ]

Heliographic chart. See under Chart. [ 1913 Webster ]

n. 1. [ Helio- + -graphy. ] The description of the sun. [ Webster 1913 Suppl. ]

2. The system, art, or practice of telegraphing, or signaling, with the heliograph. [ Webster 1913 Suppl. ]

3. An early photographic process invented by Nicéphore Niepce, and still used in photo-engraving. It consists essentially in exposing under a design or in a camera a polished metal plate coated with a preparation of asphalt, and subsequently treating the plate with a suitable solvent. The light renders insoluble those parts of the film which is strikes, and so a permanent image is formed, which can be etched upon the plate by the use of acid. [ Webster 1913 Suppl. ]

4. Photography. [ Archaic. ] R. Hunt. [ 1913 Webster ]

n. [ Gr. 'o`ros mountain + helio- + -graph. ] (Photog.) A camera for obtaining a circular panoramic view of the horizon. The photographic plate is placed horizontally with a vertical lens above. A mirror of peculiar shape reflects light from the entire horizon to the lens, by means of which it is focused upon the plate. [ Webster 1913 Suppl. ]

n. [ Photo- + heliograph. ] (Physics) A modified kind of telescope adapted to taking photographs of the sun. [ 1913 Webster ]

n. (Astrophysics) An apparatus for making spectroheliograms, consisting of a spectroscopic camera used in combination with a telescope, and provided with clockwork for moving the sun's image across the slit. -- Spec`tro*he`li*o*graph"ic a. [Webster 1913 Suppl.]