31. All comets were discovered whilst examining photographic plates taken by the Bache or Metcalf telescopes. 32. In 1880 George Eastman began to manufacture gelatin dry photographic plates in Rochester, New York. 33. He measured the magnitudes of about 130 quasars from a large number of photographic plates . 34. As the slit passed the lens, it " wiped " the exposure onto the photographic plate . 35. After returning to his home institute in Kiev, Churyumov examined all the photographic plates more closely. 36. Nancy Van Meter makes cyanotypes, created by laying an object directly on a sensitized photographic plate . 37. He asked her to place her hand on a photographic plate and switched on the machine. 38. The star was then located on photographic plates from the Palomar Sky Survey taken in 1951. 39. Marsden said an early priority will be to search photographic plates for evidence of the object. 40. Subsequent exposures on the same photographic plate are made while the object is subjected to some stress.
