Abstract
PHOTOGRAPHY has already proved of great service to astronomy, and its value in reproducing with un failing accuracy and permanently preserving an observation is evident. It is long since the art has been utilised in the observation of eclipses; with De La Rue's photographs of the moon we are all familiar, while those of sun-spots have recently attained a rare degree of per fection. And now at last photography has been success fully applied to comets by Dr. Janssen at the Meudon Observatory, Paris. The woodcut we give to-day of Comet B is from our French contemporary La Nature, and has been revised by Dr. Janssen himself, so that it may be accepted as a faithful reproduction of his photo graph. Dr. Janssen also gives scire interesting details as to the circumstances under which the pliotograph of the comet was taken. It was obtained on July 1, 1881, at oh. 37m. under the following conditions:—The operators used a telescope of half a metre aperture and 1.60m. focal length. The plates of gelatino-bromide of silver, extra sensitive, were manipulated and developed in darkness. The time of exposure was thirty minutes. Arrangements were made to counteract the proper movement of the comet in addition to the diurnal movement. The impression of the tail extends to more than 21/2 degrees; and the head of the comet assumed very great dimensions; but the details of the tail show that the move ment of the instrument has kept pace with that of the object. The rectilineal rays are a revelation of the photograph, which more over shows some very small stars not seen in any celestial atlas.
Article PDF
Rights and permissions
About this article
Cite this article
Photograph of Comet B, 1881. Nature 25, 132 (1881). https://doi.org/10.1038/025132a0
Issue Date:
DOI: https://doi.org/10.1038/025132a0