Photography of the Skies 



telescope at Arequipa, in Peru. Its light is so 

 faint that no telescope in existence is powerful 

 enough to disclose the tiny orb (Fig. 87). 



Where direct vision is easy, the camera enables 

 the photographer to save time in an astonishing 

 way. Professor Common's photograph of the 

 moon, taken in forty minutes, rewarded him with 

 as full detail as had four years' work with the 

 telescope and pencil. Often an image seen only 

 in part in the telescope is completed with won- 

 derful beauty in the camera. The streaming 

 tail of a comet is frequently doubled or trebled 

 in length as it imprints itself upon the gelatin 

 plate. Brooks's comet of 1893, in one of its 

 photographs taken with the Willard lens at Lick 

 Observatory, showed its tail as if beating against 

 a resisting medium, and sharply bent at right 

 angles near the end, as if at that point it en- 

 countered a stronger current of resistance. 

 Many nebulae, those of the Pleiades especially, 

 appear in much greater extent and detail in a 

 photograph than to an observer at the eye-piece 

 of a telescope. Their rays are particularly rich 

 in the vibrations which affect the sensitive plate, 

 but to which the eye is irresponsive.* 



More than once a word has been said about the 

 unsuspected worth of the incidental; celestial 

 photography supplies a capital illustration. In 

 1882, at the Cape of Good Hope, when the great 



* Address by Professor E. E. Barnard as vice-president of 

 Section A, mathematics and astronomy, American Asso- 

 ciation for the Advancement of Science, 1898. 

 83 



