First 100 years

Zvjezdarnica at Popov Tower – A Century in Service of Astronomy

Tatjana Kren, prof

At the turn of the 19th and 20th centuries, when the Zvjezdarnica of the Croatian Natural History Society was established at Popov Tower, Zagreb became a modern political, cultural, and economic center of Croatia, especially its northwestern parts, which were increasingly connected with European trends. Along with the development of industrialization, Zagreb achieved significant progress in the process of creating a modern civil society. It was home to the headquarters of leading political parties, and it was where the most famous political figures, writers, artists, scientists, and journalists lived. Newspapers and other public media, as well as professional and scientific literature, influenced the formation of public opinion. Every seventh resident of Zagreb was a student in primary or secondary schools or a university student.

The Founding of Zvjezdarnica and Its First Decade of Operation

Until the 19th century and the development of modern astronomy, Croats had a large number of famous scientists and philosophers in their history who studied astronomy and achieved valuable results, from Herman of Dalmatia in the 12th century to Ivan Vitez of Sredna (15th century), Franjo Petriš (16th century), and Ruđer Bošković (18th century).

In 1885, university professor Spiridion Brusina, along with his colleague and friend Đuro Pilar and a few other colleagues, founded the Croatian Natural History Society in Zagreb, the first society of natural scientists in Croatia and generally in the Slavic south. It was established at a meeting held on December 27, 1885, in the National Museum at Demetrova Street No. 1 in Zagreb’s Upper Town, and Brusina was elected as its first president. The society gathered scientists as well as laypeople of various professions who were enthusiasts of natural sciences. Regular members came from various Croatian cities, but among them were also members from outside Croatia: from Vienna, Arad, Budapest, Sarajevo, Prague, Milanovac, and Belgrade.

In its early years, the Croatian Natural History Society had two sections: geographical and ornithological, and astronomy was present in the activities of individual members of the society. Society member Dr. Oton Kučera was the author of a very popular astronomy book, Our Sky. Oton Kučera was the initiator of the establishment of Zvjezdarnica and its first director until 1913.

In 1902, a separate astronomy section was established with the goal of founding a public astronomical observatory for scientific and professional work and the popularization of astronomy. The society established the Committee of the Croatian Natural History Society for the organization of an astronomical observatory in Zagreb and appealed to the people, the city, and the government for financial support to purchase the main telescope and organize the observatory. The committee’s president was the society’s president, Dr. Dragutin Gorjanović, and its members included Dr. Oton Kučera, Dr. Franjo Spevec, the famous Croatian writer Ljubo Babić – Ksaver Šandor Gjalski, Dr. Antun Heinz, and Franjo Šandor. The committee quickly succeeded in almost completely fulfilling all the set tasks: securing funds for the first investment through a donation from the city council and contributions from citizens, acquiring the best possible main telescope (from the company Reinfeld and Hertel in Munich, manufactured in 1901, with an objective aperture of 6.4 inches or 162.6 mm), finding a suitable location for the observatory (the old city defense tower from the 13th century, Popov Tower), and obtaining the location from the city (on February 2, 1903, the city council decided to cede Popov Tower to the society for the needs of the observatory), constructing a movable dome for the telescope, and ensuring that the construction of the observatory was carried out according to strict scientific requirements.

At the beginning of 1905, Zvjezdarnica received a photographic camera, an astronomical clock, and a micrometer, and it collaborated with several European observatories. Two observatories in Germany offered scientific collaboration. That year, sunspots were studied, and a solar eclipse was observed, but the scientific results were very limited, as were those in the following years, although the observatory’s instrumentation was somewhat expanded. The failed attempt to establish a chair of astronomy at the University of Zagreb in 1906 also had a negative impact. In 1909, an attempt was made to build a new observatory, exclusively for scientific work, in Prozorje near Dugo Selo, which did not succeed. In contrast to the limited scientific work, the efforts to promote astronomy were very successful. The observatory was visited by numerous citizens and school groups from Zagreb and other parts of Croatia.

Max Wolf, director of the Heidelberg Observatory, in agreement with the discoverer August Kopff, named the asteroid 589, discovered in 1906, “Croatia” in honor of the opening of the Croatian Zvjezdarnica.

World War I and the Post-War Years

After Kučera’s departure from the position of director in 1913, the society decided to organize Zvjezdarnica primarily for the popularization of astronomy and halted all expenses for the expansion of the observatory. Along with the director, Dr. Vladoje Drapczynski, only Miro Mance worked at the observatory. Observations of planets and time determination continued, as did the reception of visitors.

At the beginning of World War I in 1914, the work of all societies was halted, and Zvjezdarnica was closed. The society entrusted Professor Adam Kugler with the care of the observatory’s inventory, and from 1915, he was also the head of the Astronomy Section. He organized the meridian circle and regularly determined the exact time, and despite the war, in 1918, he printed a movable star map published by Zvjezdarnica, the first of its kind in Croatia and the Slavic south.

In the spring of 1917, Zvjezdarnica was open for a few months, and Kugler managed to print the astronomical calendar Bošković for 1918, the first of its kind in the Slavic south.

After the death of Professor Kugler in 1918, the management of Zvjezdarnica was taken over by Professor M. Hubej, but he also soon passed away, and in 1920, the society again invited Dr. Kučera to take over the management of the observatory. Kučera was initially assisted by technical students Franjo Bošnjaković and his son, Vlaho Kučera, and later Dr. Vladoje Drapczynski returned. With the support of the government and voluntary contributions, the instruments were repaired. The greatest success continued to be in the promotion of astronomy among the Croatian population.

The Bošković calendar was published regularly until 1926 when it ceased publication due to financial difficulties. After A. Kugler, it was edited by Željko Marković, and Kučera for 1924, 1925, and 1926.

Work at Zvjezdarnica continued almost exclusively with the reception of visitors, lectures, and observations of celestial objects. In 1923, on the 20th anniversary of Zvjezdarnica and Kučera’s second term as director, it was recorded that 2,100 people visited the observatory, and students were received in groups. It was open three times a week, and on Sundays, regular observations of the Sun were held, which testifies to the great activity at the observatory, but such activity lasted only as long as Kučera managed it.

From Kučera to the End of World War II
Under the Management of the Geophysical Institute

 

In 1926, Kučera definitively left all public work, and he passed away five years later, in 1931, in Zagreb. Zvjezdarnica came under the management of the Geophysical Institute and was mostly closed to the public for a number of reasons. The director of Zvjezdarnica was the director of the Geophysical Institute, Stjepan Škreb, who was among those who believed that the observatory was not suitable for scientific work and should serve the teaching purposes of the University. Shortly after, it was concluded that the observatory was not suitable even for that purpose, and in 1937, the meridian circle and pendulum clock were transferred as a loan to a specially established institute in Maksimir.

Zvjezdarnica housed the headquarters of the Croatian Natural History Society (HPD) and its Astronomy Section, and society meetings were held there, but the observatory itself was mostly closed to visitors. As Dr. Slavko Rozgaj noted, the reason for this should be sought in the misunderstanding of Zvjezdarnica as a cultural factor by those who were first called to strengthen its role.

 

Stjepan Mohorovičić, today recognized worldwide as the “father of positronium,” the son of Andrija Mohorovičić, gave lectures on Radio Zagreb in 1932: On the Moon, its origin and structure, and The Sun and Its Nature, which is one of the indicators of the presence of astronomical topics in the Croatian public and interest in astronomy in the 1940s. From Stjepan Mohorovičić, we also learn the following interesting fact from August 1937: “…a multitude of people, armed with ‘all possible’ optical aids, observed the starry sky in the evenings in Zagreb on the surrounding hills, looking for a comet, and the newspapers later reported on it, as well as its photographs, all of which contributed to the spread of interest in astronomical sciences among wider circles.” In 1936, the Peltier comet was at its brightest during the solstice and did not attract much attention, but the Finsler comet, which S. Mohorovičić wrote about, was at its brightest during the first quarter of the Moon and could be observed excellently. Therefore, its appearance attracted the attention of a large number of interested observers, especially since, as Mohorovičić wrote, the last decade had been very scarce in such phenomena.

Zvjezdarnica During World War II

During the war years, from 1941 to 1945, in the Independent State of Croatia, Zvjezdarnica was closed, and one of its first collaborators, Miro Mance, sided with those who believed that the time of Zvjezdarnica at Popov Tower had passed. He wrote during those years: “Private observatories, whether of individuals or societies, will always be subject to various adverse influences. This experience has been confirmed in the foreign world, so I believe that it is not worth supporting them with regard to permanence and a development worthy of permanence.” He believed that a university observatory should be established, and that the instruments could be taken from Popov Tower, while the main part should be obtained by dividing the instruments received from Germany as war reparations, which the Kingdom of Yugoslavia had given to the University of Belgrade and which were then unused. However, due to the war circumstances, nothing was done.

Revival in the Work of Zvjezdarnica

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After the end of World War II and the formation of federal Yugoslavia, the Croatian Natural History Society and Zvjezdarnica of the HPD soon resumed their activities. On June 28, 1945, the Astronomy Section was re-established, and on July 9, 1945, it organized a public observation of a solar eclipse from Marulić Square in Zagreb, in the presence of a large number of Zagreb citizens. On July 11, 1945, the Astronomy Section became the Astronomy-Geophysics Section, with the task of popularizing these sciences through lectures and sky observations. Dr. Leo Randić was elected as the head, and Ivan Jurković as the secretary. Committee members included Dr. Gabrijel Divjanović, who, as a young partisan officer, participated in a kind of popularization of astronomy among partisans. He wrote a small popular astronomy book, Earth and the Universe. The booklet went through three editions and had a huge print run of one hundred thousand copies, which, regardless of the circumstances in which the new communist government tried to prove itself as a people’s government in this way, certainly testifies to the great interest in astronomy in the Croatian people in those post-war years.

Zvjezdarnica was officially reopened on August 13, 1945, by the then president of the Croatian Natural History Society, Dr. Fran Tućan, and the head of the Astronomy-Geophysics Section, Dr. Leo Randić, presented the development of astronomical work in Yugoslavia. On August 27, an astronomy course began, as well as sky observations on Wednesdays and Saturdays. Among the course participants, voluntary collaborators were selected, as is still customary today, and that year, a special course in practical astronomy was held for them. Under the leadership of the director of the Geophysical Institute, Dr. Josip Goldberg, a course for astronomy teachers in secondary schools was held, and on December 19, 1945, a lunar eclipse was observed. A projection apparatus was acquired for the needs of lectures, and lectures for the public began to be held by younger collaborators, students, and high school students.

For the first time, Zvjezdarnica was managed by the committee of the Astronomy-Geophysics Section, and in 1947, when the section was divided into Astronomy and Geophysics, the director of Zvjezdarnica became Prof. Juraj Golubić (1947–1949), who took the initiative to repair the main telescope and the leaking dome. The biggest problem was the broken mechanism for the automatic movement of the telescope, which could not be repaired, so manual tracking of objects had to be done, which made observations difficult. Interest in astronomy was great, and the number of registered visitors exceeded three thousand annually.

Abolition of Astronomy Teaching in Secondary Schools

By a decision of the Ministry of Education, in the 1948/49 school year, astronomy (along with religious education) was abolished as a subject in secondary schools. This relegated astronomy in Croatia to the position of an insignificant and unnecessary science, and all this, as Dr. Slavko Rozgaj noted, in the year when the largest telescope in the world was installed at Mount Palomar (USA). The relocation of Professor Golubić from Zagreb was also unfavorable for Zvjezdarnica, as it was left for some time in the care of a few young collaborators.

The Work of Zvjezdarnica in the Post-War Years

After Professor Juraj Golubić left the position of director of Zvjezdarnica, it was managed by Dr. Slavko Rozgaj (1949–1953), and his deputy was Zlatko Britvić, then a student at the Faculty of Natural Sciences and Mathematics. They organized the active collaborators of Zvjezdarnica, and life at the observatory began to return to normal. Each week, various professional issues were discussed at the meetings of the active members, and reports were presented. A special course on the method of observing sunspots was also held. Zvjezdarnica then, together with the Department of Dynamic Astronomy and Astrophysics of the Faculty of Natural Sciences and Mathematics, took on the obligation of regular solar observations and the submission of observations to the international institution for solar physics in Zurich. These observations were led by Zlatko Britvić.

On April 2, 1950, a very well-attended observation of a total lunar eclipse (about 4,000 people) was organized from Vraz Promenade, and that year, Zvjezdarnica was visited by 11,000 people. Zvjezdarnica began a successful period of popularizing astronomy despite unfavorable conditions and the marginalization of astronomy. The income of Zvjezdarnica was realized through a subsidy from the City National Committee of Zagreb (G.N.O. Zagreb) to the Croatian Natural History Society and voluntary contributions from visitors, as entrance fees were not charged.

In May 1953, Milan Butorac organized an exhibition at Zvjezdarnica as an introduction to the celebration of the half-century of Zvjezdarnica, with the theme of the development of astronomy, where all available astronomical literature in Croatian was displayed, as well as the instruments of Zvjezdarnica. A darkroom for developing photographs was set up, a celestial globe was obtained, materials for the construction of two reflector telescopes, a radio set, and a large number of books and sky maps were acquired. The G.N.O. Zagreb awarded Zvjezdarnica, in addition to the regular subsidy, an extraordinary financial aid for the arrangement of the premises and instruments and the preparation of the astronomical exhibition, so Zvjezdarnica was closed for four months for renovation. That same year, Zvjezdarnica received funds for the purchase of a Zeiss telescope of 4 inches, thus solidly marking the half-century since its opening, and Dr. Slavko Rozgaj, satisfied with the achievements, then wrote:

“As long as there is understanding for the ideal goals of its collaborators, it will continue to spread its influence further and stronger, until the last member of our nation feels completely and consciously a citizen of the universe.”

In 1953, Rozgaj had to leave the management of Zvjezdarnica, which was temporarily taken over by Zlatko Britvić, then a student, and then from 1954 by Dr. Gabrijel Divjanović. Dr. Slavko Rozgaj, recorded as the author of very successful astronomy books Astrognosy, The Book of Stars, and others, continued to work as a high school teacher until his retirement.

 

Zvjezdarnica During Divjanović’s Management

Orientation Towards Flammarion and Kučera

In 1954, the management of Zvjezdarnica was entrusted to Dr. Gabrijel Divjanović, who marked almost a quarter of a century of its operation (1954–1978). Zvjezdarnica focused primarily on the task of popularizing astronomy among the people and successfully carried out this task, and alongside popularization, professional work also began to develop more strongly, i.e., work on observations and measurements, which were carried out by young participants in astronomy courses held for high school students. At Zvjezdarnica, several specialized groups operated, such as the Sun group, the variable stars group, the visibility group, the astrophotography group, the radio astronomy group, the astronautics group, and others.

Pacifism and Esperanto

A group of young people from Divjanović’s period was also enthusiastic about pacifist ideas. Together, they wrote a science fiction work, initiated by G. Divjanović, Drama in the Universe. The booklet was printed in 1960 (second edition in 1966, and the third in the scientific-popular journal Nature of the Croatian Natural History Society in 1995). During those years, the universal world language Esperanto was learned at Zvjezdarnica, and Drama in the Universe was already printed in Esperanto translation in 1961 as Tragedio en la Universo. At Zvjezdarnica, an astronomical-Esperanto radio station operated during those years – a member of the Radio Club Zagreb, the only one of its kind in the world.

In 1961, the international Esperanto-astronomical Camp of the Friends of Peace was established in Primošten with the Tourist Observatory, where astronomers and Esperantists from all over the world met.

Summer astronomy camps continued with the organization of camps, in cooperation with the “Science to Youth” Movement and the Astronomical-Astronautical Society of the SR Croatia, on Cres, Hvar, Mali Lošinj, Fažana, and then to this day in Prvić Luka near Šibenik, with the exception of the war years 1992, 1993, and 1994, when the camp was held in Trakošćan.

Zagreb Planetarium

All types of planetariums, from the simplest to the most modern, are very successful tools in the popularization of astronomy, as well as in education. The Zagreb Planetarium is located on the first floor of the Technical Museum in Zagreb. It was acquired by the HPD, its Astronomy Section, and Zvjezdarnica in 1965, marking the 80th anniversary of the Society. However, although small, this Zeiss planetarium, of which a large number can still be found in Europe and the world, could not be placed at Popov Tower due to lack of space. Therefore, it was placed in the Technical Museum, where it still operates today.

New Telescope

In 1964, Zeiss exhibited a 5-inch refractor at the Autumn Fair, which in size completely matched the dome at Popov Tower. Its characteristics were 130:1950, long-focal, ratio 1:15. The objective was designed for visual observations. It had six eyepieces with magnifications of 31, 49, 78, 122, 195, and 327 times, filters, an eyepiece spectroscope, and a circular micrometer, as well as a number of other auxiliary devices. It is very suitable for amateur work. The Croatian Parliament took over the costs of purchasing this refractor as a recognition of Zvjezdarnica for its work with youth on the occasion of the 60th anniversary of Zvjezdarnica.

Before installation, the old dilapidated dome had to be renovated, and a new concrete base for the new refractor had to be made, and the company “Laboratoria,” through which the telescope was purchased, could not immediately take over the instrument after the closing of the Fair because the foreign currency funds were blocked due to the expected increase in the value of the dollar. The first problem was solved by the voluntary work of amateur astronomers, who made the concrete foundation, painted, repaired the internal wooden paneling, various devices, doors, windows, repaired and painted the entire Zvjezdarnica. The telescope was finally successfully delivered to Zvjezdarnica on December 11, 1965, and installation began at the end of 1966.

Journal Earth and the Universe (Man and the Universe) and the Publishing Activity of Zvjezdarnica

In Divjanović’s period, the journal Earth and the Universe was launched in 1956. From 1956 to 1958, the editor-in-chief was Oliver Wittasek, and the responsible editor was Leo Randić. It was a journal with a small circulation until 1968/69, when Gabrijel Divjanović took over as editor-in-chief and soon created a high-circulation scientific-popular journal. In 1970, he changed its name to Man and the Universe, in line with his thoughts on a humanistically engaged journal, and under this name, the journal began, along with purposeful propaganda, an exceptionally successful journey throughout SFR Yugoslavia, reaching a circulation of 70,000 copies in 1971, which was a lot for an astronomical journal even by world standards, and certainly showed the great interest of the broadest layers in astronomy. It sold exceptionally well in Serbia, especially in Vojvodina and Kosovo, as well as in Macedonia. The journal was translated into Esperanto and under the title Homo kaj Kosmo (1963–1986), it was read for years in Esperanto circles almost all over the world.

In 1973, Tatjana Kren’s publication Nikola Copernicus and His Work was published at Zvjezdarnica, the text of a lecture given at the celebration of the 500th anniversary of Copernicus’s birth at the Technical Museum in Zagreb.

In 1974, along with the scientific-popular journal Man and the Universe, the journal Bolid was launched at Zvjezdarnica, the journal of the Astronomical-Astronautical Society of the SR Croatia (AAD SR Croatia), a journal for the publication of observational and other works in astronomy. The idea and editor of Bolid was Gustav Kren. Bolid filled the gap left by the cessation of the publication of the Bošković Almanac, as it soon began to publish once a year the Small Astronomical Yearbook for the following year, so amateur astronomers once again received the basic data needed for astronomical observations.

In 1975, Gustav Kren and Tatjana Vranić – Kren printed the first wall map of the starry sky in SR Croatia, published in five editions. It was followed by the Map of the Solar System (Gustav Kren, Tatjana Vranić – Kren, and Čedomir Igaly).

In the period of Zvjezdarnica’s management, Zlatko Britvić initiated the publication of a series of Seminar Papers. Number 1 in the series was the publication: Zlatko Britvić: Optical Astronomical Telescopes, 1981, followed by: Zlatko Britvić: Elongations and Phases of Planets and the Moon, Davorin Kresonja: Astronomical Visibility, and in 1982: Čedomir Igaly: Computer Atlas of the Sky and Zlatko Britvić: Sundials.

In the 1980s, as special editions of the journal Bolid, the following booklets were published: Željko Andreić: Amateur Telescope Making, 1984; Goran Ivanišević: The Dictionary of Extragalactic Astronomy Terms, 1985; Gustav Kren (ed.): XIX Youth Astronomy Camp. Prvić Luka 16-26.07.1987. Collection of Lectures, 1987; Željko Andreić: Astronomy for the Youngest; Tatjana Kren: Observations of Astronomical (Celestial) Phenomena in the Proverbs of Our People. A Study of Proverbs with Astronomical Themes, 1989; Roman Brajša, Gustav Kren, Dragan Roša, Vladimir Ruždjak, Bojan Vršnak: Our Star the Sun, 1990; Goran Ivanišević: Lexicon of Extragalactic Astronomy, 1991; and Valter Martinolić: Choosing Telescope Magnification, 1992. As a special double issue of the journal Man and the Universe, the booklet Halley ’86 was printed in 1986.

In 1993, the book General Astronomy, Part I by Drago Roša was published by Zvjezdarnica, followed by A Look into the Cosmic Ocean (ed. Zdenko Marković), a commemorative publication on the occasion of the 90th anniversary of Zvjezdarnica in Zagreb 1903–1993, and Drago Roša: General Astronomy, Part II, 1995.

Inclusion in the World Celebration of the Birth of Nikola Copernicus

 

 

 

 

 

 

 

Inthe 70th year of Zvjezdarnica’s operation, 1973, it joined the world celebration of the 500th anniversary of the birth of Nikola Copernicus. In cooperation with the Technical Museum and the planetarium director, Ante Radonić, an exhibition was opened, and Tatjana Kren gave a lecture at the Technical Museum on the life and work of the famous Polish astronomer. The Polish Astronomical Society “Nikola Copernik” awarded the medal of Copernicus to the president of the Yugoslav Academy of Sciences and Arts (JAZU) Grga Novak and three collaborators of the Zagreb Zvjezdarnica: Dr. Žarko Dadić, Zlatko Britvić, and Dr. Gabrijel Divjanović for their special merits in the celebration of Copernicus’s jubilee. Gustav Kren modeled the Copernicus plaque, which was sent to Poland, to the Copernicus Museum, and in an interesting way, the 83-year-old amateur astronomer Stjepan Ivanek from Zagreb paid tribute to Copernicus by constructing a small hand-held planetarium, the Copernican System.

In the 1970s, occasional exhibitions were held at Zvjezdarnica, such as an exhibition dedicated to the Croatian astronomer Dr. Slavko Rozgaj and the Russian astronomer Vorontsov-Veliaminov, conceived by Dr. Goran Ivanišević. During those years, Zvjezdarnica was visited by famous world astronomers: E.R. Mustel, M.S. Zverev, G.P. Kuiper, and W. Zonn, which was very important for the affirmation of Zvjezdarnica in a professional sense.

Encouraging Amateur Astronomy

Zvjezdarnica already in 1955 encouraged the establishment of a branch of the Astronomy Section in Samobor, the first branch outside Zagreb, and then from 1963 to 1965 helped to establish astronomy sections in Dubrovnik and Šibenik. The Astronomical Society “Faust Vrančić” in Šibenik has been continuously operating since 1965 as an astronomy section, and after 18 years of work, the section grew into the Astronomical Society “Faust Vrančić” Šibenik in 1984, and is the oldest astronomical society outside Zagreb. The establishment of branches marked the beginning of the branching of astronomical activity from Zvjezdarnica throughout Croatia.

In 1971, the Astronomical-Astronautical Society of the SR Croatia (AAD SRH) was established at Zvjezdarnica, as a continuation of the Astronomy Section, in the new circumstances of Zvjezdarnica as an independent institution, which separated from the Croatian Natural History Society. AAD SRH began to develop cooperation with amateur astronomers in Croatia, gather them, and stimulate the establishment of new astronomical societies. The journal Man and the Universe was very important in establishing communication. In cooperation with Zvjezdarnica, the Society organized astronomy courses for students, for which there was always great interest, and in 1971, a record of over 700 participants in courses from the Zagreb area was recorded. Due to inadequate space for such a large number of students, two or three parallel courses were held.

Participation in Competitions of the “Science to Youth” Movement

Collaborators of Zvjezdarnica, under the leadership of Dipl. Ing. Zlatko Britvić, prepared young amateur astronomers, students of primary and secondary schools, for participation in the Republican and Federal Competitions in Astronomy of the “Science to Youth” Movement, where they were at the top of the competition results for years. Young collaborators of Zvjezdarnica were also active in observing permanent and occasional celestial phenomena: lunar and solar eclipses, the appearance of supernovae, comets, the transit of Mercury in front of the solar disk, and others, and in 1971, the organization of meteor expeditions began, which are very interesting, especially for young amateur astronomers. Much attention was paid to cooperation with amateur astronomers from foreign countries, and collaborators of Zvjezdarnica participated in several international congresses of amateur astronomers. Particularly good cooperation in that period was achieved with Hungarian amateur astronomers.

At the end of the 1960s, a workshop operated in the ground floor of the building at Opatička 22, where amateur astronomers ground mirrors and made parts for their own telescopes.

Collaborators of Zvjezdarnica and members of AAD SR Croatia participated in professional work and observations of the Sun and other celestial objects at the Hvar Observatory of the Faculty of Geodesy of the University of Zagreb, established in cooperation with the Academy of Sciences of the CSSR. Within the framework of the exchange of experts for personal improvement, they stayed at the Ondřejov Observatory near Prague.

Astronomical Expeditions Outside SFRY

In 1961, a total solar eclipse was observed from Hvar, successful photographs were taken, and published in the booklet ABC Solar Eclipse February 15, 1961, by Milan Butorac.

In 1966, the first astronomical expedition outside SFR Yugoslavia was organized, to Turkey, to observe an annular solar eclipse (May 20, 1966) in Ayvalik (Turkey). Ten years after the first expedition to Turkey, in 1976, Stjepan Šuntić, then president of AAD SRH, organized, in cooperation with Zvjezdarnica, an expedition to Turkey, again to observe an annular solar eclipse. The following year, 1977, Stjepan Šuntić organized the expedition “In the Footsteps of Galileo” to Italy, whose participants visited the great Italian observatories, which was very useful in a professional sense, especially for young participants, who had the opportunity to see the equipment of large professional observatories. Along with amateur astronomers, awarded correspondents of the journal Man and the Universe participated.

In 1980, Zvjezdarnica and the Astronomical-Astronautical Society of the SR Croatia organized an expedition to the solar eclipse of February 16, 1980, in Kenya, and in 1986, an astronomical expedition to follow Halley’s Comet was organized, to Aswan (Egypt), where a small Croatian team (Zdenko Marković, Gustav Kren, and Darko Dragojević) flew by plane, together with two other teams from the former Yugoslavia, Sarajevo (Muhamed Muminović and Milorad Stupar) and Novi Sad, led by Jaroslav Francisti.

The Return of Zvjezdarnica to the Croatian Natural History Society

Dr. Gabrijel Divjanović left the management of Zvjezdarnica in 1978, retiring, and the new director became Zlatko Britvić, Dipl. Ing. Geodesy (1978–1981), who tried to change the traditionally established concept of Zvjezdarnica, which led to numerous disagreements and problems and finally forced administration over Zvjezdarnica. By a decision of the Zagreb City Assembly, the forced administrator in 1983 became Dr. Nikola Ljubešić, a biologist from the Ruđer Bošković Institute, who made great efforts to overcome the crisis situation. From July 1, 1984, the management of Zvjezdarnica was again taken over by the Croatian Natural History Society.

In 1980, an interesting exhibition of children’s works on space themes was organized at Zvjezdarnica, dedicated to the “Year of the Child,” under the title Children and the Universe, by Maja Šuveljak.

In 1981, due to the new way of financing societies, the Union of Astronomical Societies of the SR Croatia (SAD SRH) was established, and the former AAD SRH retained this name in the Zagreb framework as the Astronomical-Astronautical Society Zagreb (AAD Zagreb). That year, on the date of the founding of Zvjezdarnica, December 5, the Day of Astronomy was organized for the first time, a review of Croatian amateur astronomers, organized in separate societies.

Celebration of the 80th Anniversary

On the occasion of the 80th anniversary of Zvjezdarnica, an exhibition on the work of Zvjezdarnica from 1903 to 1983 was set up with the help of members of the Astronomical-Astronautical Society Zagreb, and the exhibition was supplemented with their works by members of astronomical societies from Čakovec (Strahoninec), Rijeka, Pitomača, Pula, Šibenik, Virovitica, and Višnjan. The celebrations were attended by numerous guests, members of astronomical societies, and citizens. The welcoming speech was given by Dr. Nikola Ljubešić, and the lecture on the past eighty years of Zvjezdarnica was given by Tatjana Kren. Speeches on the work of Zvjezdarnica were given by Dr. Pavle Gregorić, Dr. Gabrijel Divjanović, and Prof. Dr. Leo Randić.

New Times and New Conditions

Renovation of Popov Tower

Although the care of Zvjezdarnica was entrusted back to the Croatian Natural History Society (HPD) in 1984, Zvjezdarnica was soon granted autonomous status within the Society, which significantly contributed to solving the problems of renovating its premises and activities.

In September 1984, work began on the renovation of the Zagreb City Museum, which included the renovation of Popov Tower. Construction work made observations and public lectures difficult. Under very challenging conditions, with scaffolding and limited access to the terrace, many Zagreb citizens still observed Halley’s Comet from Zvjezdarnica from late 1985 until April 1986, when access to the observatory terrace became completely impossible.

Throughout this period, the Zagreb City Museum and some other groups waged an incomprehensible and illogical battle to remove Zvjezdarnica from Popov Tower, disregarding its cultural and historical significance for Croatian culture and science. However, the Zagreb City Assembly and the Scientific Research Council of the Republic of Croatia provided funding for the renovation of the observatory terrace and new premises in the attic of the building at Opatička Street 22. Thanks to the beginning of the renovation of the Upper Town, Zvjezdarnica finally received a modernized space, a new dome, and necessary equipment.

Zagreb Observatory in the Republic of Croatia

In 1990, Zvjezdarnica faced the multi-party elections closed to the public due to construction work, with its telescope dismantled. However, it continued its work in popularizing astronomy through its journals Man and the Universe and Bolid, as well as through constant contact with interested citizens and lectures for school groups. Members of the Astronomical-Astronautical Society Zagreb (AAD Zagreb) organized sky observations for the public on several occasions in Zagreb using portable telescopes.

In 1992, a new dome was installed on the renovated terrace, and due to a lack of funds, the old Zeiss refractor was returned to service.

From 1984 to 1993, Zvjezdarnica was formally managed by the Croatian Natural History Society without a designated director. In 1993, Mr. Dragan Roša, MSc, who had been a staff member at Zvjezdarnica since 1986, became its head. This was visibly reflected in the more independent operation of Zvjezdarnica and its shift toward new projects, in line with the times.

The 90th anniversary of Zvjezdarnica was celebrated in 1993 with the “Days of Croatian Astronomy” at the observatory, featuring numerous events. A traditional gathering of generations was also held, with many participants.

The following years were marked by preparations for the celebration of the 100th anniversary, with an emphasis on the achievements of the information age in which we live.