Photography of the Skies 



death-blow at that time, for it showed the utter 

 inability of the average astronomer to sketch or 

 draw under such circumstances what he really 

 saw." Compare the pencil with the camera in 

 one of its recent achievements. On January 22, 

 1898, Mrs. Maunder with a lens only one and a 

 half inches in diameter, secured impressions of 

 swiftly moving coronal streamers about five 

 million miles in length. It is evident enough 

 that the pencil cannot compete with the camera 

 in depicting the extremely brief phenomena of an 

 eclipse, and it is also plain that an instrument of 

 moderate size and cost is quite sufficient for 

 good work. 



Often the images of the telescope are not fleet- 

 ing, and remain visible quite long enough for a 

 draughtsman to catch their outlines; but other 

 circumstances than those of time forbid the use 

 of his pencil. Professor E. E. Barnard has taken 

 observations at the Lick Observatory when the 

 thermometer has stood at 32 C. At such a 

 temperature a camera may be used, while to 

 employ a pencil is out of the question. 



In many tasks, where extremes of cold or 

 heat do not trouble him, the astronomer is glad 

 to avail himself of the quickness of the sensitive 

 plate, which so far transcends the celerity of the 

 eye. If in its rapidity of response a quick plate 

 is superior to the retina, it has the further advan- 

 tage of being exempt from fatigue. Light 

 much too feeble to excite vision can impress an 

 image on a sensitive plate if it is given time 

 79 



