Our Astronomical Column

Abstract

ADVANCES IN LUNAR PHOTOGRAPHY.—MM. Lœwy and Puiseux recently communicated to the Paris Academy a paper on photographs of the moon, taken at the Paris Observatory, by means of the great Condé equatorial. Some of the photographs have been enlarged by Dr. Weinek, and the enlargements seem to have excelled in beauty and detail previous lunar pictures of a similar kind. An examination of the photographs shows that not only can they be used to verify the general features of the moon' surface, as depicted upon the most recent and complete lunar maps, but they also show a number of details and small craters which so far have been omitted from such maps. There are, of course, a number of causes which prevent a single photograph from being an ideal representation of a celestial object, and enlargements are usually regarded with a certain amount of suspicion, for there is always a possibility that interesting formations will be unconsciously manufactured in the process. MM. Lœwy and Puiseux know this as well as anyone; nevertheless, they find that the enlargements undoubtedly reveal new features, and definitely determine the existence of several contested objects. They think an instrument of long focus is essential for the best results, and that the enlargements should not be carried beyond twenty or thirty diameters. One object upon which the photographs have thrown light is the small isolated crater Linné, situated in the middle of the Sea of Senenity. According to Shroeter, Beer, Maedler, Lohrmann, and other selenographers, this crater was distinctly visible up to 1866, when Schmidt announced its disappearance. It was afterwards discovered again, but was much smaller than when described and figured by Beer and Maedler. Dr. Weinek finds that the object appears upon a plate taken on March 14, but only one kilometre in diameter—that is, about one-tenth the value assigned to it by the earlier observers. The crater has also been found on other plates, and Sig. Schiaparelli has testified to its reality. Four new objects—three craters, and the fourth an isolated elevation of some kind—have been found in the plain which extends to the south of Ariadaeus, between the bright craterplain Cayley and the Silberschlag crater. Ten new craters can be detected in the typical walled plain Albategnius. All the rills observed to the weat of Triesnecker can be seen to extend beyond the limits previously assigned to them, and to connect Ariadaeus, Hyginus, and Triesnecker with interlacing clefts. Judging from these results, we cannot but conclude that the photographs represent real advances in lunar photography.