The earliest astronomers had only their eyes with which to observe space. When astronomers like Galileo, Huygens, and Newton first began to use telescopes, they would meticulously draw their observations onto paper. As technology progressed, new methods to record images and data were developed. Beginning in the nineteenth century, photographic plates became the main recording media of astronomical data for more than one hundred years. In the late-twentieth century, photoelectric detectors and computer-based digital cameras replaced photographs. This is the technology by which almost all telescopes today record their data.