WEDNESDAY, APRIL 13th, 1892. 
SOME OF THE MORE REMARKABLE 
RESULTS OBTAINED BY THE USE OF 
PHOTOGRAPHY IN ASTRONOMICAL 
RESEARCH ; 
(With Illustrations by the Electric Lantern), 
BY 
MR. EDWARD ALLOWAY PANKHURST. 
The rise of astronomical photography may be said to date 
from 1839, when Daguerre took a picture of the moon by the 
wonderful process of light printing which he discovered. The 
next year the great astronomer Arago, who foresaw in a measure 
the aid which the new process would bring to astronomy, 
presented to the Academy of Scienees a negative of the moon 
much superior to Daguerre’s. Great difficulties however stood 
in the way of complete success. The old wet process demanded 
an exposure of twenty minutes even for the moon. Moreover, the 
mechanician had not yet perfected those clocks which regulate 
the movement of the telescope, and which, keeping time with 
such wonderful aecuracy with the motion of the earth, enable 
astronomers to keep any sidereal object he may wish to observe 
or photograph undeviatingly in the centre of the field of his 
optic tube. 
In 1851 the collodion process was discovered, and almost 
simultaneously the driving mechanism of the telescope was 
greatly improved. The result was that in 1853, Warren de la 
Rue, with his 13 in. reflector, obtained some remarkable results 
in lunar photography. Astronomers were not able to avail 
themselves of all the advantages which large refractors possess 
for photographing the heavenly bodies on account of the optical 
difficulties connected with the process. The focus of the actinic 
rays is not the same point as that of the visual rays. Dr. 
Rutherford, however, overcame this difficulty by grinding his 
lenses so as to meet the exigencies of the case, and in 1864 was 
rewarded for his trying work by obtaining photographs of the 
moon which still excite our admiration. 
