Clyde Tombaugh, an American astronomer, used this method in 1930 to find Pluto. The blinking technique involved taking two photographs of the same region of the sky taken at different times. When the two images were rapidly alternated, any object that had moved between the exposures would appear to blink or jump. This allowed Tombaugh to sift through the vast amount of stars and identify the faint, moving object that was Pluto.
