Introduction

BULGARIAN NATIONAL ASTRONOMICAL OBSERVATORY - ROZHEN

Latitude: +41° 41' 35.00'' - Longitude: +24° 44' 38.00'' - Altitude: 1759 m

The National Astronomical Observatory - Rozhen is the biggest observatory in Southeast Europe. It was opened in February 1981. This is one of the largest investments Bulgarian science has ever made. The observatory has three night telescopes: a 2-meter Ritchey-Chretien-Coude (RCC) telescope, a 50/70-cm Schmidt, and a 60-cm Cassegrain telescope. A solar telescope was also built, that is used for observing the Sun, with a wide range of applications in the field of solar physics. A multifunctional infrastructure has been established in the observatory.

The IA and NAO employ about 50 astronomers who are working in the following fields of research:
• Small bodies in the Solar system (physics and chemistry of asteroids, comets, planet satellites);
• Solar astrophysics (computer simulations of active processes, magneto-hydro-dynamical modeling);
• Stellar astrophysics (symbiotic stars, peculiar stars, cataclysmic variables, flare stars)
Extragalactic research (active galactic nuclei, large scale structures in the Universe, cosmology).

The history of astronomical research in Bulgaria may be divided in two periods: before and after 1981, when active astronomical observations started in the Rozhen NAO. This has led to an exponential growth of new astronomical findings in Bulgaria and has placed us among the countries with established traditions in the field of astronomy. The observatory is situated at an altitude of 1759 meters in the western central Rhodope Mountain. Its position has been chosen to fit the specific requirements of astronomical observation: an observatory should be situated far from towns and villages to avoid any light pollution; it should be at a high altitude and in a place with a high percentage of nights suitable for observation purposes.
Forty new variable stars of the anti-dwarf novae type have been found at the observatory. There have been researches on star explosions and variability of stars due to stellar spots. Extragalactic observations have been made that show the existence of super clusters of galaxies. A foundation has been laid for the research of small bodies in the Solar system (asteroids and comets). As a result of this more than a hundred new asteroids have been found and some of them have been given Bulgarian names. At the end of 1985, when Halley’s comet visited Earth again, the first successful observations of the comet in Europe were done with the largest telescope in the Rozhen NAO (with a primary mirror of 2 m in diameter).
When the observatory was starting its work, many young astronomers were invited to participate in the preparation process and in the observations themselves. Many of those who made their first steps in professional astronomy here, at the Rozhen NAO, are now eminent scientists in Bulgaria and abroad. The equipment at the Rozhen NAO is being used for dozens of international projects, involving astronomers from Germany, France, Italy, Poland, Russia, Finland, Belgium, Turkey and Macedonia. Most of the findings made have been widely acknowledged and published in journals of international repute. Every year Bulgarian astronomers are invited to participate in different international conferences. Students of Bulgarian and foreign universities participate in seminars and have the opportunity to work with professional astronomy research equipment.