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 ]