The “Observatorio del Roque de los Muchachos” (ORM) on La Palma and the “Observatorio del Teide” (OT) on Tenerife, combine world class facilities for night and solar time studies. At present, there are telescopes and other astronomical instruments from nineteen countries (Armenia, Belgium, Denmark, Finland, France, Germany, Ireland, Italy, the Netherlands, Norway, Poland, Portugal, Russia, Spain, Sweden, Taiwan, Ukrania, the United Kingdom, and the United States). This group, together with the scientific and technical facilities of the “Instituto de Astrofísica de Canarias” in Tenerife, constitute the European Northern Observatory (ENO), shortly to be boosted by the coming into service in 2003 of the 10.4 m optical-infrared Gran Telescopio Canarias (GTC) and with the facilities of the Joint Astrophysics Centre (La Palma).