Chemical Elements as Tracers of the Evolution of the Cosmos


Rozhen National Astronomical Observatory, Institute of Astronomy and National Astronomical Observatory (Smolyan, Bulgaria)


The Institute of Astronomy and National Astronomical Observatory (IA and NAO), Bulgarian Academy of Sciences is the largest scientific organization dealing in astronomy in Bulgaria. NAO Rozhen is an observational facility of the Institute located in Rodopa mountain, Southern Bulgaria, 250 km from Sofia. It is the largest astronomical complex in south-eastern Europe and a major training centre for graduate and PhD students of astronomy in the region.

NAO Rozhen has three telescopes for optical observations of comets, asteroids, stars, star clusters and galaxies and a telescope for observations of the Sun.

The largest telescope is the 2-meter telescope system Ritchey-Chretien Coude. It is equipped with fiber-fed echelle spectrograph ESpeRO, Coude spectrograph and 2-channel focal reducer FoReRo. The benchmark of the current astronomical epoch is the great advance in spectroscopy, chiefly through the use of modern echelle spectrographs and CCD detectors, coupled with the advances in numerical stellar atmospheres models. The high resolution spectrographs are used mainly for precise radial velocity measurements, chemical abundances and pulsational behavior studies of stars. Besides the opportunity to gather high resolution spectra with ESpeRo and FoReRo, we can obtain low resolution spectra of weaker objects by using the focal reducer FoReRo. The other valuable mode of FoReRo is the polarization mode through which we can make polarimetric observations of comets and stars.

Over the past almost 40 years since the 2-m telescope has been operational, the host equipment was continually updated to maintain the effectiveness of its work. The control system of the telescope was completely renovated 10 years ago under the funding of Bulgarian National Scientific Fund. In 2017 the main mirror of the telescope was recoated successfully in Germany.

NAO Rozhen has two other smaller telescopes: the 50/70 cm Schmidt telescope and the 60 cm Cassegrain telescope. Both telescopes are equipped with modern CCD cameras together with UBVRI, Sloan (ú', g', r', i', z') filters, as well as other narrow-band filters, including Hα filter for obtaining photometric data.

The presence of three telescopes at the observatory allows synchronous monitoring of one and the same object simultaneously in two or more optical fields or simultaneous spectral and photometric observations.

Services currently offered by the infrastructure

We offer the echelle spectrograph EspeRO and the Coude spectrograph. ESpeRo is a bench mounted instrument with temperature and humidity controlled environment. It is able to provide in one hour exposure a high resolution spectrum, R=35000, and S/N ratio of about 80-100 for 9-th magnitude star. The spectral region covered is 3900 to 9000 Å. The magnitude limit is about 13-th magnitude. The uncertainties of radial velocities derived at proper and rich in absorption features regions are well below 1km/s. The Coude spectrograph allows to obtain high-resolution spectra with R=30000 and 15000 with spectral range of a single spectrum of about 200 Å and 100 Å respectively. The limit magnitude is about 12-th magnitude.

Currently, NAO-Rozhen operates in visiting mode, demanding the observing astronomer to be at the telescope.

Linked ChETEC institution

Web pages

ChETEC contact person

  • Ivanka Stateva (