Tähtitieteellinen yhdistys Ursa

Ursa Astronomical Association

The Ursa shop at the Helsinki Observatory is currently open on Tuesdays, Thursdays and Fridays from noon to 4 pm.

Ursa Astronomical Association is the oldest and largest amateur astronomy association in Finland with circa 19 000 members across the country. Ursa's primary focus is to spread information about astronomy and amateur astronomy and offer an up-to-date, comprehensive view of the universe to its members and the general public. Ursa's mission is to provide information in Finnish, but we will gladly answer any questions also in English.

The Ursa Office

The Ursa office in Helsinki is located at Helsinki Observatory, 2nd floor. Books and published by Ursa and a selection of high quality binoculars and telescopes are available for purchase. The staff can be reached by telephone (int. +358 9 684 0400, dom. (09) 684 0400), e-mail ursa(a)ursa.fi, or regular mail (Ursa Astronomical Association, Kopernikuksentie 1, FIN-00130 Helsinki, Finland). A large number of books and magazines are mailed annually.

History of Ursa

Tähtitieteellinen yhdistys Ursa (Ursa Astronomical Association) was founded in 1921 by Yrjö Väisälä and several other young scientists. Five years later Ursa established an observatory in southern Helsinki (Kaivopuisto Park). In the beginning, activities included public lectures on astronomy and related sciences. In the 1930s Ursa released two films dealing with astronomy and the theory of relativity. In the late 1960s Ursa obtained a small room from the City of Helsinki which was used mainly as a library and was open twice a week.

From the 1930s to the 1960s several members of Ursa edited books published by a commercial publishing house. In 1975 Ursa published its first book. Nowadays Ursa is the most notable astronomy book publisher in Finland.

Ursa's membership journal Tähtiaika was first published in 1971, and it was renamed Tähdet ja avaruus in 1976. The journal got its first full time employer in 1998 and it was renewed into modern astronomy magazine. Nowadays Tähdet ja avaruus has a staff of four, circulation of 18 750 and about 75 000 readers.

History and Services of the Ursa Library

The Ursa Library was founded in the mid-1920s. For a long time the library had less than a hundred books. The number of items began to grow in the early 1980s. Members can borrow books, offprints, slide sets, video films and audiotapes by visiting the library in person or sending their orders via mail. The current library collection consists of nearly 8 000 items in about 20 languages. About 3 500 are books, excluding bound volumes of magazines. The majority of items are in English, Finnish, German or Swedish. A catalog of items is available either in printed or electronic form. Since late 1997 the catalog has been available for browsing from the Ursa web site. Members and other users of the Ursa Library borrow over 1 000 items annually.

Ursa Observatory

The Ursa Observatory is in Kaivopuisto Park in Helsinki. Three telescopes are available for use. A very old Merz refractor was bought in 1928 (aperture 135 mm, focal length 1950 mm), and is still in excellent condition. A 25 cm Ritchie-Chretien reflector shares the mounting with the Merz-refractor. A fairly new Celestron 8 telescope is on a separate mounting. The observatory has a small warm room that has enough space for four or five persons. The Merz-refractor can be used with a narrow wavelength Hydrogen-alpha filter. Nonmembers can visit the observatory during autumn and spring evenings to look at the starry sky, and during the day on summer weekends to observe solar phenomena through filters. Interested members can use the observatory on Mondays and times outside of star shows.

The public shows are (clear weather only):
15 Oct-15 Dec: Tue-Sun at 7 to 9 PM
15 Jan-15 Mar: Tue-Sun at 7 to 9 PM
15 Mar-15 Jun: Sun at 1 to 3 PM
1 Aug-30 Sep: Sun at 1 to 3 PM

5 € adults, 2 € children, free entry for members and preschoolers


Ursa members first designed and developed a portable planetarium in 1984. Its plastic dome is six meters in diameter and over four meters high, and it can accommodate about 20 people during presentations. Two kinds of projectors are available: they can present the starry sky, Sun, Moon, planets and twilight. Slides can also be projected onto the dome. The planetarium has been exhibited at fairs, and many schools in southern Finland have used the planetarium for an entire day or more. Ursa also has two Star Lab planetariums available for schools to rent at a modest cost.

Lectures, Courses and Events

The work of Ursa has included public lectures for several decades. During spring and autumn months, three to five lectures are held. They are open for anyone interested, free of charge. Lecturers include both professional astronomers and experienced amateurs. Topics include the results of new studies, fundamentals of astronomy, or current events in the sky. The lectures are in Finnish.

Ursa also arranges several courses annually on evenings or weekends. One of the most popular courses discusses how to use telescopes. The courses are in Finnish.

Ursa cooperates with local (independent) astronomical associations each year during Astronomy Weekend. The first Astronomy Weekend was held in Turku in 1971. Active amateurs and members of the general public are welcome to attend. The program typically consists of lectures, planetarium shows and exhibitions.

Since 1987, Cygnus Summer Meetings have been held each year for active amateurs. This is generally a four-day long event, and includes meetings of Ursa sections, photo contests, discussions, observations, and telescope making.

For several years the Astronomy Day in winter or autumn has also been held, when many associations arrange astronomical programs for less-experienced amateurs or interested laymen. These events include lectures, exhibitions, slide and video shows, star shows without fees, etc.

Ursa maintains contact with all amateurs' associations in Finland. A database of associations is updated frequently.

Activities for Young People

Many of Ursa's over 18 000 members are young people. An annual astronomical youth camp is organised each summer, sometimes also during the winter months. Several clubs for children and teenagers gather every week at Helsinki Observatory (outside of the Summer months and a month long Christmas break). In the clubs, kids become acquainted with astronomy and observing. They can also visit the planetarium and the exhibition in the building. If weather permits and the sky is dark enough, telescopes are carried outside for observing.


Ursa is the most notable Finnish publisher of popular science books dealing with astronomy and related sciences, several of which have been awarded. Ursa also publishes the popular astronomy magazine Tähdet ja avaruus.


Taivaanvahti is a free to use observing service for everyone.The concept of the service is simple: users can upload their observations of celestial phenomena, often accompanied by photographs, and view the observations made by others. Via the service, users can check whether someone else spotted that fireball last night or whether someone photographed that magnificent display of northern lights. Since its inauguration in the autumn of 2011, the service has attracted thousands of users.

Sections and working groups

There is so much to observe that it is not possible for one person to effectively observe all kinds of phenomena. Ursa has 16 observing and technical sections and working groups: The Sun; Observation instruments; Atmospheric optics; Club and association activities; The Moon, planets and comets; Mathematics and information technology; Meteors; Storm chasing; Minor planets and occultations; Aurorae; Deep sky; Satellites and rocket phenomena; Variable stars; CCD-observations; Weather and observing conditions and Weather calendar.

All sections help to coordinate the work of amateurs, giving advice and collecting observations. Sections also interact with each other and have cooperating activities. The most important form of cooperative activities is the Cygnus summer meeting.