D - F.

De La Rue, Warren (1815-1889) - British astronomer who was one of the first to use photography in astronomy. He photographed the Moon and developed a device to photograph the Sun. While observing a total solar eclipse he determined that prominences were part of the Sun, not the Moon.

Dolland, John (1706-1761) - eighteenth century English telescope maker who claimed to have invented the achromatic lens, which eliminated chromatic aberration from telescopes. His telescopes were highly prized by astronomers of the time.

Draper, Henry (1837-1882) - American astronomer who in 1872 became the first person to photograph the spectra of a star (Vega) other than the Sun. After his death his widow bequeathed his instruments and some money to Harvard Observatory in order to continue his work. In 1890 the first Henry Draper Catalogue of stellar spectra was published.

Dreyer, John Louis Emil (1852-1926) - in 1888 published the New General Catalog of the positions of over 13,000 nebulae, galaxies, and star clusters that can be found in the night sky.

Eddington, Arthur S. (1882-1944) - in 1924 he established a link between a normal stars luminosity and mass. This relationship applies only to average main sequence stars, not stars at the beginning or end of their lives.

Encke, Johann Franz (1791-1865) - German astronomer who was the second person to predict the return of a comet. Encke's comet has a period of only 3 years, using this comet the mass of Mercury was estimated in 1835.

Erastosthenes - Greek scientist, who was one of the first to attempt to determine the size of the Earth and came remarkably close to the actual number. Also was the first to determine the obliquity of the ecliptic.

Eudoxas (408-355 BC) - Greek mathematician who was the first to describe a theoretical explanation of the movements of the planets. Each planet is attached to differing spheres which revolve around the Earth as its center. Each sphere is tilted in respect to the earth, thus accounting for the motions of the planets as seen in the night sky. He calculated there to be 26 spheres.

Euler, Leonhard (1707-1783) - mathematician and scientist who studied and attempted to explain the motions of the Moon. He published several tables of the perturbations of the Moon using advanced mathematical models.

Fabricus, David (1564-1617) - best known for an observance he made in 1596 of a star in the constellation of Cetus. The star (later named Mira) was the first variable star to be discovered in modern times.

Fallows, Fearon (1789-1831) - the first director of England's Royal Cape Observatory in South Africa. From this vantage point he catalog the positions of over 4000 stars visible in the Southern Hemisphere.

Flammarion, Nicolas Camille (1842-1925) - French astronomer who claimed to have detected changes in craters on the Moon, which he believed was caused by vegetation. He helped to popularize astronomy in the nineteenth century with is book Popular Astronomy.

Flamsteed, John (1646-1719) - in 1675 he became the first Astronomer Royal of England when he was placed in charge of the newly created Greenwich Observatory. He completed a catalog locating the positions of over 3000 stars (the best of its time) titled Historia coelestis Britannica.

Fleming, Williamina Patons Stevens (1857-1911) - devised system to classify stars based upon their spectra which was published in 1890 as the Draper Catalogue of Stellar Spectra. In 1907 she published a list of 222 variable stars she discovered and in 1910 she published her work on the discovery of white dwarf stars, she was the first to identify them.

Foucault, Bernard Leon (1819-1868) - proved the rotation of the Earth by hanging a pendulum from the ceiling of the Pantheon in Paris in 1851. The pendulum's plane of oscillation rotated throughout the day, thereby proving the rotation of the Earth.

Fraunhofer, Joseph (1787-1826) - German optician and telescope maker. While studying sunlight through a spectroscope he plotted 574 lines, since known as Fraunhofer lines. He also saw similar lines from reflected moonlight and coming from the star Sirius. He used his knowledge of the spectrum to create the best achromatic lenses for telescopes available. He is also credited with designing the first equatorial mount for a telescope.