Ramsden, Jesse - English telescope maker of the late 18th and early 19th centuries. His telescopes were in high demand by astronomers of the time. Riccioli, Giovanni Battista (1598-1671) - Italian astronomer who is credited with naming many features of the Moon, including naming the craters after famous scientists. He was also the first to observe a double star through a telescope. Rittenhouse, David (1732-1796) - American clock and instrument maker and astronomer who observed the transit of Venus in 1769 from his Pennsylvania farm. He is considered by many to be the father of American astronomy. Roche, Edouard (1820-1883) - demonstrated that a moon is limited in its orbit around a planet. If the moon passes within a certain distance (Roche Limit) it will be torn apart by the gravitational interactions between itself and the planet. Romer, Ole (1644-1710) - Danish astronomer who is credited with the invention of the transit telescope in 1689. By observing the Galilean satellites of Jupiter he came to the conclusion that light travels at a finite speed, and was one of the first scientists to attempt to calculate it. Russel, Henry Norris (1877-1957) - in 1913 plotted a two-dimensional diagram of the absolute magnitude versus spectral type for stars. In 1911 it was also independently created by Ejnar Hertzsprung. The diagram today is called the Hertzsprung-Russell (H-R) Diagram and is an invaluable tool to astronomers.