Writing and Reading

      Astronomers have come up with several creative ways to deal with problems of magnification. One technique is to make the telescope larger. A larger telescope collects more light from the object, producing a brighter image. Another solution is to use a recording device, such as a photographic film or an electronic detector. These methods have an advantage over the human eye: observations of faint objects can be made over a very long time. The exposures can be as long as 45 minutes per image. Multiple images can be added together to produce effective exposure times of up to 38 hours for each filter. The longer an exposure is, the more light falls on the film. As long as the image is held very still, an image of even a faint target will eventually appear.

The writer is considering deleting the underlined sentence.
Should the sentence be kept or deleted?