: an optical instrument by means of which two pictures identical in all but a few details (such as two images of the sky taken on successive nights) may be registered in a single visual field and viewed alternately in rapid succession                                      
              
                             Tombaugh then used a blink comparator, a device that compares two plates and highlights moving objects. One moving speck turned out to be Pluto.—
Nancy L. Hendrickson,                Astronomy,                November 1998                          
                
                     
            
   
                   
             
                    
                        
        
        
        
                
                
                
        
                
     
    
                                                    
                                                                                                                                                
            
                                    
                        
                                                    
                                
                       
                                        
                
                                                
                            
            
                                    
                                    
                        
                                            
                                                            
                                    
                                                                
                                
                
                
                
                
                
                
                
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
                                        
                                                    
                            
                                                               
                                                
  
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  Merriam-Webster unabridged
 
                          
                    
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