Astronomical Observatory
About
In Transylvania, the study of stars goes back to the 15th century. The activity of Ioan Vitéz of Zredna (1408-1472), bishop of Oradea, is worth mentioning as he was in touch with famous astronomers of the time, such as Peuerbach and Regiomontanus. The Transylvanian humanist Johannes Honter (Honterus, 1498–1549) presented in his geography book, Rudimenta cosmographica (Krakow, 1530), the description of the universe according to Ptolemy's vision. The appearance of comets or the meteor showers, spectacular astronomical phenomena but also frightening for those times, were mentioned in books published in Transylvania by Gaspar Heltai, Wilhelm Misocacus or Stephanus Wolphard. Astronomy papers were published in the 17th century by Izrael Hübner and Samuel Kaposi.
In 1581, Stephen Báthory, Prince of Transylvania and King of Poland, established the Claudiopolitan Academy in Cluj, and following a papal act issued in 1583 by Pope Gregory XII a Jesuit seminary was attached to the Claudiopolitan Academy. With the development of the university, the field of natural sciences is becoming more and more important. The research tradition mentioned above prompted the urgent need to set up an astronomical observatory in Cluj. The development of studies and research in Astronomy, as well as the design and planning for the construction of an astronomical observatory in Cluj were made possible by two Jesuit monks: Nicolaus Ianosi (1701–1741) and Maximilian Hell (1720–1792).
The Jesuit monk Nicolas Ianosi, originally from Cluj, became a professor at the University of Cluj (1734–1739) after completing his studies in Vienna. During the above mentioned period, he established high-quality astronomy studies and initiated the first plans for a future astronomical observatory. The Jesuit monks appointed Maximillian Hell to come to Cluj in 1752 to continue the building of the astronomical observatory.
(1720-1792)
Hell designs a new plan for the astronomical tower and orders personally the high-performance astronomical equipment from Vienna. Throughout the years he spent in Cluj, Hell taught mathematics and astronomy at the Academia Claudiopolitana (by then Universitas Claudiopolitana) and began writing a series of monographs entitled Elementa mathematica naturali philosophiae ancillantia. Unfortunately, Maximilian Hell could not see his dream of having an astronomical observatory materialize at the University of Cluj because in 1755 he was recalled to Vienna, where he became director of the Imperial Astronomical Observatory, achieving remarkable scientific results in astronomy.
The work started by Ianosi and Hell was completed by Nandor Hartmann, a mathematics teacher who lived in Cluj between 1755 and 1769. With the completion of the new building of the university, the astronomical tower which housed the astronomical equipment (mobile quadrant, astronomical clock and telescope) brought especially from Vienna was also built. Unfortunately, on 31 August 1798 a strong fire devastated the centre of Cluj, causing great damage to the university and the astronomical observatory. The rebuilding of the university and of the new astronomical tower was laborious, and the astronomical tower remained standing until 1893.
Several years after the great union of 1919, plans of a new astronomical observatory in Cluj were resumed.
(1881-1941)
In 1920, the construction of a new and modern astronomical observatory started in Cluj on a practical and convenient site located on the (then) outskirts of the city. The Astronomical Observatory in Cluj was built between 1921 and 1934 on the site of today's “Sigma Center” (the name of the Observatory street was given precisely by the Astronomical Observatory, which operated here until 1977, when it was demolished and on its site was built the “Electrosigma” industrial ensemble).
(1885-1969)
The initiative for building a new observatory came from George Bratu, mathematics professor, dean and vice-dean of the Faculty of Sciences, director of the Observatory of Cluj between 1919-1920 and 1928-1941. The first specialized scientific equipment: a Newtonian reflector telescope (50 cm mirror diameter), a Prin equatorial telescope (20 cm lens) and many astronomy books were commissioned through the efforts of Professor George Bratu and Professor George Demetrescu (director of the Observatory between 1921-1928). Since 1982 the Observatory operates in a new building located in the south side of the “Alexandru Borza” Botanical Garden.
The material assets purchased in 1982 consisted of: a Coudé-Zeiss refractor (150/2250) (located in the 600 cm Gautier-Prin dome), a Zeiss refractor (100/1000), a Zeiss sextant and a Zeiss theodolite. This equipment was added to the already existing one from the interwar period, which had acquired by then a heritage status (the above mentioned Newtonian telescope and the Prin telescope). In the 80s the Observatory was equipped with: 130 mm Reinfelder refractor, 15 cm “Vierlinser” astrograph (quadri-lenticular lens), 70 mm Frauhoffer refractor, a ‘lunette de passage” (for observing the celestial bodies crossing the local meridian) and a universal instrument (theodolite). From 2007, in a joint financial effort (of the Romanian Government and of UBB) the material assets of the Observatory have been expanded with the addition, following the purchase and installation, of a new 450 cm dome (PD 15 Technical Innovations), which houses a 30 cm Meade Schmidt-Cassegrain catadioptric refractor and a Coronado solar refractor equipped with a 60 mm Hydrogen Alpha bandwidth filter. Other purchases included: a SBIG spectrograph, CCD cameras of various types, a 26 cm Vixen reflector telescope installed in parallel with the Coude instrument in the old dome, telescope accessories, and a computer network. The Observatory owns a specialized library, which contains over 16,000 titles and is open Monday to Friday from 9.00 to 15.00.
The astronomy classes are open to students of the Faculty of Mathematics and Computer Science and of the Faculty of Physics. The fundamental elements and specific elements are learned on the spot, where students participate in courses, seminars and laboratories. The activity within the Observatory is integrated in the research seminars on the topic “Celestial mechanics and space research” and “Structure and evolution of stars”, in research grants, in published journals and books, as well as in national and international workshops organized annually.
Since 2008 the Observatory organizes activities for the general public also. Visitors are welcome every Friday night, after dark, for a visiting tour of approximately 2 hours. It consists of an introduction (projecting a simulated configuration of the sky map of the moment accompanied by an explanation of the celestial objects that will be observed), and a practical, observational activity, using the existing equipment. (Ferenc Szenkovits)Open hours
Every week since 2008, on clear Friday evenings after dark, the Astronomical Observatory has been open to the public. The entry fee is 20 lei. Admission is free for UBB students and staff with a valid student ID or employee ID. School students and students outside Babes-Bolyai University benefit from 50% deduction
We would like to inform the public regarding several noteworthy astronomical events in the coming days:
- 19 April 2026 – Comet C/2025 R3 (PANSTARRS) reaches perihelion – may be visible to the naked eye;
- 9 June 2026 – Venus and Jupiter will be visible in the western sky after sunset;
- 12 August 2026 – partial solar eclipse, visible from Cluj as the sun sets;
- 12-13 August 2026 – peak of the Perseid meteor shower, new moon, good viewing conditions after midnight;
- 28 August 2026 – partial lunar eclipse visible from Romania will occur during the second half of the night;
- 12 October 2026 – the small planet Vesta is in opposition, bright and easy to spot;
- 2 December 2026 – Mars and Jupiter are within 5 degrees of Regulus after midnight;
- 7 January 2027 – the dwarf planet Ceres is in opposition, bright and easy to spot;
- 2 August 2027 – partial solar eclipse visible from Cluj, covers 30% of the Sun;
- 10 October 2027 – Venus and Mercury will be visible after sunset;
- Lunar occultations of planets and bright stars.
During the Alternative School Week and Green Week, the Astronomical Observatory is open to organised groups of students who wish to take their first steps into exploring the secrets of the Universe and the Earth, all week, including Saturdays and Sundays. Teachers accompanying the students are kindly requested to contact the observatory staff in advance to schedule a visit and to bring groups of no more than 35 students.
Main equipment
1. Meade RCX400 catadioptric reflector
| Parameters | Specs |
|---|---|
Optical design |
Advanced Ritchey-Chrétien |
Aperture |
305 mm (12″) |
Lens focal length |
2438 mm |
Focal ratio (exposure time) |
f/8 |
Separating power (angular separation) |
0.375″ (arc seconds) |
2. Coude Refractor 2250/50 mm
| Parameters | Specs |
|---|---|
Optical design |
Coude |
Aperture |
150 mm (12″) |
Lens focal length |
2250 mm |
Focal ratio (exposure time) |
f/15 |
Separating power (angular separation) |
0.9″ (arc seconds) |
3. Coronado SolarMax 60 mm solar refractor
| Parameters | Specs |
|---|---|
Optical design |
Meade refractor |
Aperture |
60 mm |
Lens focal length |
400 mm |
Focal ratio (exposure time) |
f/6.6 |
4. Vixen VMC260 reflector
| Parameters | Specs |
|---|---|
Optical design |
Modified Cassegrain design |
Aperture |
260 mm (12″) |
Lens focal length |
3000 mm |
Focal ratio (exposure time) |
f/11.5 |
Separating power (angular separation) |
0.45″ (arc seconds) |
Limiting magnitude |
13.8 |
History
The First Astronomical Observatory in Cluj-Napoca
Directors of the Astronomical Observatory:
| Name | Period |
|---|---|
1920-1923, 1928-1941 |
|
1922-1928 |
|
1941-1945 |
|
1945-1954 |
|
1954-1977 |
|
1977-1992 |
|
Professor Vasile URECHE (born 1934) |
1992-2000 |
Professor Vasile POP (born 1940) |
2000-2005 |
Associate professor SZENKOVITS Ferenc (born 1959) |
2005-2024 |
Associate professor Cristina BLAGA |
2024-today |