Space discovery

At the end of nineteenth century, astronomy stood on the threshold of a great revolution . although it was one of the oldest of the sciences, progress in astronomical studies before the twentieth century remained mostly confined to observations in the visual light using ground-based optical telescopes. No doubt several small and large observatories has come up during the eighteenth and nineteenth centuries, but the real breakthroughs came only in the twentieth century with the discovery of a host of strange astronomical objects that no one could imagine existed. Not only did optical telescopes become bigger, with greater power to capture faint starlight, but novel detection methods also came up to extend our reach to the fastest limits of the cosmos.

Thus the twentieth century witnessed enormous advances in observational techniques as well as scientific understanding of the physical progresses that shape the cosmos, one of biggest innovations during the twentieth century was in the design and construction of telescopes. Although Newton had built his first reflecting telescope in 1672, not many large reflectors for astronomical observation were built till the twentieth century. The main problem was that large diameter glass mirrors had to be thick for dimensional stability, which increase their weight tremendously and made them difficult to maneuver. Secondary, the front surface silver coating easily got tarnished and needed frequent re-coating. To wards the end of the 1930s, two new discoveries emerged that revolution telescope making. The first was a method of depositing aluminum, rather then silver, on to glass mirrors.