ASTRONOMICAL PHOTOGRAPHY 761 



Since the total duration of eclipse phenomena including both partial phases will 

 last for something like 4 hr., it is obviously a waste of time and film to photograph the 

 partial phase continuously in the kinematograph. A single exposure with the motion- 

 picture camera made at hi- or ^i-min. intervals is entirely sufficient in the partial 

 phase. An exposure once in 8 sec. has also been frequently used. In any of these 

 procedures an abundant amount of film will result for educational or entertainment 

 purposes in depicting the progress of the phenomenon. It is necessary, of course, if 

 satisfactory registration is to be obtained, that the motion-picture camera be fixed to 

 an equatorial mounting driven by clockwork to follow the movement of the sun during 

 the interval. A guiding telescope for checking the registration continuouslj' is also 

 desirable. It is hardly necessary to remark that the guiding telescope should be 

 provided with a dense dark glass in front of the eyepiece for the proper protection of 

 the eyes of the observer. 



Bibliography 



Stetson, H. T.: On an Apparatus and Method for Thermoelectric Measurements for Photographic 



Photometry, Astrophys. J., 43 (Nos. 4 and 5) (1916). 

 : Investigations of Plate Errors with the Thermo-electric Photometer, Astrophys. J., 68 (No. 1) 



(1923). 

 King, E. S.: "A Manual of Celestial Photography," Eastern Science Supply Company (1931). 



: Standard Tests of Photographic Photometry, Harvard Observatory Ann., 59. 



Ross, F. E.: "Physics of the Developed Photographic Image," Eastman Monograph 5. 



