Christiaan Huygens and his brother create the first powerful Keplerian telescope with an objective diameter of 2.24 inches and a focal length of 12 feet. He used this device to discover Titan, the largest moon of Saturn, and the tenth largest object in the solar system. He also used the same telescope to observe the Orion Nebula with enough precision to observe individual stars. Finally he used his telescope to study the rings of Saturn, and to create theories on what they were. He went on to publish his findings in Systema Saturnium, which included drawings of the Orion Nebula and characteristics of and an explanation for the rings of Saturn.