Advances in Astronomical Technology^ 



By Aden B. Meinel 



Director, Steward Observatory, University of Arizona 



[With 4 plates] 



Astronomy is a branch of science that has contributed much to the 

 rapid expansion of the frontiers of modern technology. The unique 

 technical problem faced by the astronomer is the f aintness of the stars 

 and other objects with which he must work. Telescope mirrors meas- 

 ured in meters across are needed to gather enough flux of this faint 

 light to permit its study. Celestial objects are also so far away that 

 their apparent size is so small that the astronomer's telescope must, in 

 addition, focus the faint light it gathers to a sharp focus. 



Most celestial objects are in reality very hot and luminous but ap- 

 pear faint because of their great distances from us. The brightest 

 star, Sirius, with an intrinsic luminosity 28 times that of our sun is 

 approximately 10,000 million (1 followed by ten zeros) times appar- 

 ently fainter than the sun, and it is one of the closest of the visible 

 stars. The faintest galaxy of stars that can be detected with the 

 200-inch Palomar telescope is so remote that its light has taken over 

 1 billion years traveling at the velocity of light (300,000 km/sec) to 

 reach us from the depths of space. These two problems, faintness 

 and small angular size, set the unusual characteristics of astronomical 

 instrumentation and research. 



The eye is little used in astronomical work today except in the ex- 

 amination of the moon and planets. 'V\niile the eye is exceedingly 

 sensitive to light it does not have the property of integration. In 

 other words, the eye will not detect any star fainter than one it can 

 see in the first second of time. A photographic plate, on the other 

 hand, will record ihoi picture of stars 100 times fainter in 100 seconds 

 than it will record in 1 second. In recent decades the astronomer has 

 principally Avorked with the photographic process to determine the 

 position, motion, and brightness of celestial objects. Photography 

 still represents a method of information storing unrivaled for pictorial 



1 Reprinted by permission from The Indian d Eastern Engineer, 104th Anniversary 

 Number, 1962. 



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