The Observatory at Popov Toranj (Priest’s Tower) in Zagreb’s Upper Town (Opatièka Street 22) was founded through the initiative of the Croatian Society of Natural Sciences, while the City Council provided premises at Popov Toranj for the Observatory’s needs and approved funding for building renovation and installation of the astronomical telescope and dome. The Observatory was officially opened on the 5th December 1903. Oton Kuèera, the Observatory’s first director, described its main functions as follows:“Our astronomical observatory has a two-fold purpose: 1) to contribute with its instrument resources and labor force to the advancement of the science itself, and 2) to disseminate, especially among the Croatian intelligentsia and the youth, the results of that most exalted, beautiful and accomplished natural science, and become a hub for all of the Croatian people who are interested in that science.”
The international renown of the Observatory received a boost after the Heidelberg astronomer August Kopff named a newly discovered planetoid Nr. 589 (spotted in 1906) „Croatia“ in honour of the opening of the Observatory.
From the very beginning, the Observatory has intensified the work on the promotion of scientific knowledge, particularly among the public and the youth. Eventually, the popularization of astronomy and related sciences as well as permanent support for school taught astronomy has become the Observatory’s core activities since the observatories in cities gradually lost their importance as scientific observation stations. The most productive period of popularization began in 1950s after Gabrijel Divjanoviæ was entrusted by the Croatian Society of Natural Sciences with the care of the Observatory. For nearly three decades he played an important role in improving the promotion of astronomy and expanding the activities of the Observatory, which became known around the world due to its publications in Esperanto. The journal Man and Universe (Homo kaj Kosmo), the young astronomers’ SF work Drama in Space (Tragedio en la Universo), the publications on the International Friends of the Peace (Astronomical Esperanto) Camp organized in Primošten, etc. have been translated into Esperanto. These actions were also part of the wider effort for humanization of science.
In a time of ever increasing interest in astronomy, due to successful flights of Soviet and American spacecrafts into space, new forms of activities have been applied: the organization of astronomy summer schools, school competitions in astronomy, camps, courses, astronomy expeditions and astronomical observations, and, in 1960s, a high quality professional and popularization work was made possible by the acquisiton of a new, electric telescope. The Observatory and the Croatian Society of Natural Sciences made their greatest cultural contribution by procuring a planetarium in 1963. It was donated to the Technical Museum, where it is still in use.
Thanks to its varied and extensive activities, the Observatory eventually became a sectional organization of the Croatian Society of Natural Sciences. In 1971, the Observatory was established as an autonomous municipal institution but, due to staff problems, was re-incorporated into the Croatian Society of Natural Sciences in 1980. The Astronomical Astronautical Society of the Socialist Republic of Croatia (later, the Astronomical Astronautical Society Zagreb – AAD Zagreb), founded within the Observatory in 1970s, attracted a multitude of lovers of astronomy and natural science, and many prominent Croatian scholars were regular visitors to the Observatory. With its traditional programs for general public (lectures, sky observations) the Observatory has become a symbol of the city’s cultural life. The Observatory has encouraged the foundation of astronomy associations across Croatia, providing them with expert and technical assistance. In the mid-1980s, during the renovation of the building complex in Opatièka Street 22, which is mainly used by the City Museum of Zagreb, the city authorities secured funds for the adaptation of a part of the premises for the Observatory’s needs. With the funds provided by the Ministry of Science and Technology the necessary work equipment was procured and a new dome was built and installed in 1992 after Croatia achieved its independence.
During those years, the first professional association of Croatian astronomers was established – the Croatian Astronomical Society. It entrusted the Observatory with the organizational care for school competitions in astronomy, and organized several seminars for teachers, scientific seminars and invited lectures at the Observatory. In 1996, the E-school project in the field of natural history, including the astronomy, was started. Unfortunately, the support of the relevant government departments was not sufficient for the Observatory to fully achieve its objectives. The Croatian Society of Natural Sciences found itself in a similar situation and, due to its modest means, it was not in position to help the Observatory. The solution was achieved thanks to the understanding and support from the City Office for Education and Sports of the City of Zagreb. Namely, in April 1999, the Astronomical Association of Zagreb (ZAS) was founded, which represents a link between amateur astronomers of Zagreb and the city system for technical education. The founding members were the Astronomical Astronautical Society Zagreb, which has been active at the Observatory for years, and the Technical Educational Association „Dr. Oton Kuèera“. They were later joined by several other organizations. At the same time, the Astronomical Association of Zagreb is the legal framework for the activity of the Zagreb Observatory. After the foundation of the Astronomical Association of Zagreb the Observatory left the Croatian Society of Natural Sciences.
After the Observatory returned under the wings of the City of Zagreb, which resolved crucial existential questions for this renown institution with a long history, the Observatory has continued to meet cultural and scientific needs of the citizens of Zagreb and the whole of Croatia, and survived as a traditional gathering point for social life of the youth interested in astronomy, astronautics and related natural and technical sciences. At the same time, the Astronomical Association of Zagreb has started the process of integrating all forms of non-professional astronomy that occur in the city – amateur, popular and academic. In 1998, the Observatory was awarded the National Award for Technical Education “Faust Vranèiæ”, and on the occasion of its 100th anniversary it was presented with the Plaque of the City of Zagreb.
In November 2007, the new telescope was installed at the Observatory, a modern apochromatic refractor with a computer-controlled assembly. The telescope was purchased with the funds provided by the City Office for Education, Culture and Sports of the City of Zagreb. Its optical capabilities are optimal for the location of the Observatory and the Observatory’s core function – the popularization of science. The telescope is furnished with additional equipment and, most importantly, it is much easier to operate. The same assemblage also incorporates the „old“ Zeiss telescope that, in 2008, is due to be equipped with instruments for patrol solar observation in the Hα line.
Besides the telescope, a cosmic ray particle detector was installed at the Observatory in 2008. It is the first instrument for the detection of cosmic radiation in the Republic of Croatia, and it is a part of an international network i.e. a project performed under the auspices of the UN. The detector was constructed in cooperation with the Cosmic Radiation Division (Aragats Space Environmental Center), Alikhanyan Physics Institute in Yerevan, Armenia, which donated all scientific equipment.
In addition to their scientific importance, both of these instruments also have an educational role. The Observatory is visited by many thousands of school children and citizens throughout the year and, thanks to the new equipment, the visitors can better experience the universe in which we all live.
A significant shift in educational projects has been achieved after Croatia started attending the International Astronomy Olympiad in 2006.