Newtonian telescope secondary mirror. This design reduces the size and cost of the telescope with a shorter overall telescope tube length (with the corrector extending the focal length in a "telephoto" type layout) combined with a less costly spherical mirror. Commercially produced versions of this design have been noted to be optically compromised due to the difficulty of producing a correctly shaped sub-aperture corrector in a telescope targeted at the inexpensive end of the telescope market. 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
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