Photochart of polar stars. 19th-century series of photographs for a region of the northern polar skies,showing some 1270 stars. Three types of photographic prints are shown here: silver bromide prints (exposed using gaslight),platinotype prints (exposed using diffused sunlight),and a photozincograph. The exposure times range from 20 to 60 seconds (silver bromide prints) and 3 to 30 minutes (platinotype prints). Two circular (polar projection) engravings are also shown. The observations were carried out by on 14 August 1888 by British amateur astronomer and engineer Isaac Roberts (1829-1904). For transparencies,see image C024/9978 | |
Licence : | Droits gérés |
Crédit: | Science Photo Library / Royal Astronomical Society |
Taille de l’image : | 4664 px × 3745 px |
Model Release : | Non requis |
Property Release : | Non requis |
Restrictions : | - |