Photographs of Comet c 1908 at the Royal Observatory, Greenwich

Abstract

LONG-EXPOSURE photographs of comet c 1908 have been obtained with the 30-inch reflector on September 6, 7, 8, 14, 17, 18, 21, 25, and 26, the exposure ranging from forty-five minutes to an hour (except on September 14 and 25, when exposures of twenty minutes were made). The comet possesses a bright tail, the structure of which is well shown in the photographs, to a distance of 1½° from the head. The appearance of the tail changes greatly from night to night, so that photographs taken at much shorter intervals than a day are desirable in order to trace the alterations in structure continuously. With this in view, on September 17 three photographs, with exposures of forty-five minutes, were taken at intervals of approximately an hour (reckoned from the middle of each exposure); decided change had occurred between the first and last photographs, and the middle photograph served to show how the transition had taken place. Efforts are being-made to obtain a series of photographs at short intervals extending throughout a night, but so far the full moon and the weather have prevented this.