Newtonian telescope Newtonian telescope The Newtonian telescope, also called the Newtonian reflector or just the Newtonian, is a type of reflecting telescope invented by the English scientist Sir Isaac Newton (1642–1727), using a concave primary mirror and a flat diagonal secondary mirror. Newton's first reflecting telescope was completed in 1668 and is the earliest known functional reflecting telescope. The Newtonian telescope's simple design makes it very popular with amateur telescope makers. Newton's idea for a reflecting telescope was not new. Galileo Galilei and Giovanni Francesco Sagredo had discussed using a mirror as the image forming objective soon after the invention of the
El Conde prior to the Teotihuacan, Toltec, Chichimeca, and certainly the Aztec. In the Mesoamerican Preclassical period (1300 to 1400 BCE), an Olmec group arrived and had a significant influence on the Tlatilca domain. Later, the Tlatilca were also heavily influenced by the Teotihuacan civilization. Between 1000 and 1200 CE, the Chichimeca conquered the Tlatilca and deposed their monarchy. The pyramid of El Conde was built during this time, located in what is now the El Conde neighborhood. Subsequently, the area was ruled by Tlacopan and ethnically came to be dominated by the Otomies. As of 1428 CE, the area was under