PHOTOGRAPHING THE STARS. 297 



without becoming blurred and indistinct. The view that 

 a photograph presents of any lunar mountain or crater, 

 cannot be compared either in beauty or in sharpness 

 with the picture that a telescope of adequate power will 

 give the eye. In fact we may certainly say that no 

 material addition to our knowledge of lunar topography 

 has been contributed by photography. We may, how- 

 ever, hope for better things ; for, with the extremely 

 sensitive plates now procurable, a picture of the moon 

 obtained under favourable atmospheric conditions with 

 an extremely short exposure might prove much more 

 capable of being magnified than any of the photographs 

 that have heretofore been taken. 



In the delineation of the planets, photography has 

 comparatively been little applied, though the attempts 

 which have been made are full of interest. The pictures 

 of Jupiter by Henry at Paris, as well as those from th 

 Lick Observatory, are excellent. The bands and other 

 markings on the planet come out distinctly, and the 

 renowned red spot is a very conspicuous object. In a few 

 photographs, taken at intervals of half an hour, the gradual 

 shifting of the features shows in an interesting manner 

 the rotation of the planet on its axis. This very rota- 

 tion is, however, one of the difficulties which impede 

 successful photography of the planet. In the course of 

 a long exposure the gradual displacement of the features 

 by the rotation precludes the possibility of a sharp and 

 well-defined picture. Here, again, very brief exposures 

 and highly sensitive plates become the desideratum of 

 the astronomer. 



\ cannot but think that photography will have a 



