5. RECENT HISTORY (1968 – 2000)

In 1968, the observatory became part of Hamburg University, which gave the observatory greater access to the wider academic community both within Germany itself, and the outside world. The contact with other departments at the university had obvious benefits, but of course the observatory also lost a certain amount of its independence, and was no longer a collection of “observators”. Among the important consequences was that directors were now elected by committee every two years, and that observatory staff became involved more deeply in astronomical teaching at the University physics department.

5.1 Astronomical Work of the observatory

As the observatory became part of the University of Hamburg, Professor Alfred Behr replaced Otto Heckmann as Director. One year later Prof Alfred Weigert joined the observatory and shared directorship with Behr through the 1970s. Behr was involved in the development of astronomical instrumentation, including a polarimeter for the new ESO. Under his direction, the Bergedorf Schmidt telescope was moved to Calar Alto, Spain and regular observations were started in 1980. Behr himself retired in 1979. Weigert was a theoretician, who headed the largest group at the observatory, working on stellar interiors and binary stars.

During the period 1968 – 2000, we may reasonably split the work of the observatory into two distinct epochs: 1970 – mid 1980s, and the mid 1980s onwards.

5.1.1 1970’s – Mid 1980’s

Towards the end of the 1960s, the importance of observations carried out at Bergedorf itself declined, and beginning in the 1970s the Bergedorf astronomers travelled with increasing frequency observatories such as ESO in Chile and Calar Alto in Spain. A consequence of this was that the astronomers no longer needed to live at the observatory, and unused accommodation could be converted into office buildings. For example, the Director’s villa was converted in 1989 to house the Extragalactic Astronomy groups (Quasars and Gravitational Lenses),22 and in 2002 the “Beamtenwohnhaus”, containing apartments for staff, was converted into offices for the Stellar Astrophysics group.

The focus of the work during this period was very much on stellar astronomy, on the observational side covering astrometry (measurement of the positions and movements of the stars), observations of “special” stars such as variables and double stars, and some solar system work on comets and asteroids. The work on astrometry ended in 2001, having been actively pursued at the observatory almost since its foundation in 1833. On the theoretical side, research covered stellar evolution and modelling of the interiors of stars. 

During this period that Bergedorf made an important step: a move away from purely optical observations (using light which the human eye can see) to the utilisation of all types of light (in scientific terms, all parts of the electromagnetic spectrum). When Professor Wendker (a radio astronomer) joined the observatory in 1972, radio astronomical work on the interstellar medium became an active area of research – solidifying the move away from purely optical astronomy.

The observatory’s work on extragalactic astronomy (the astronomy of objects which lie outside our own Milky Way galaxy) was first mentioned in the annual reports in 1973 (Jahresbericht Hamburger Sternwarte, 1973) – and this work was destined to become one of Bergedorf’s most prominent in the last decade of the 20th century. The extragalactic work started with radio astronomical observations of galaxies with the German 100m radio telescope in Effelsberg, near Bonn, and with theoretical studies of the gravitational lens effect.

In the early 1980’s there was also a brief excursion into space research with the development of an “artificial Sun” to calibrate a spectrometer for the European “Spacelab”. This was launched in 1983 on the Space Shuttle Columbia.

5.1.2 Mid 1980’s – 2000

The decision to move the Schmidt telescope to Spain and thence to begin work on a very important survey of quasi-stellar objects, or “quasars” shifted the focus of the observatory’s work in this epoch to extragalactic astronomy, away from mostly stellar research. Following the work in radio astronomy, use was made in the 1990’s of observations from satellites such as IUE and ROSAT, extending the observable electromagnetic spectrum into the ultraviolet and X-rays. Bergedorf also became a major German user of the Hubble Space Telescope. The use of satellites and ground-based observatories worldwide in all regions of the electromagnetic spectrum is now commonplace.

The work of the observatory in this period was split into roughly three broad groups: Gravitational Lenses under Professor Sjur Refsdal, Extragalactic Astronomy under Professor Dieter Reimers and Stellar Astrophysics under Professor Alfred Weigert until 1991.

The Gravitational Lenses group was formed in 1980 when Refsdal moved back into his former field of research after the first discovery of a gravitational lens in 1979. Refsdal had joined the observatory in 1970 and worked the first years with Weigert on the stellar interiors. The Gravitational Lens group focused on the determination of the Hubble constant, a parameter which determines the expansion speed of the universe, and on microlensing, which deals with the distortion of optical light of distant quasars by intervening stars. Refsdal retired in 2001 and was replaced in 2002 by P. Hauschildt, a theoretician specialized on modelling od stars and planets.  

Fig. 16. Gravitational lens HE1104-1805 discovered by the Hamburg/ESO Survey. A and B are images of the quasar. In the center the lensing galaxy (Source: CfA-Arizona Space Telescope LEns Survey http://cfa-www.harvard.edu/castles/noimages.html)

The Extragalactic Astronomy group under Reimers (who joined the observatory in May 1980) has from 1985 managed one of the observatory’s most important activities – the All Sky Objective Prism Survey, carried out at the Calar Alto observatory in Spain with the Schmidt telescope moved from Bergedorf in 1975. Known as the Hamburg Quasar Survey, this involves scanning plates (with a PDS machine purchased in 1983) taken with the telescope and identifying potential quasar candidates. A similar survey is being carried out at La Silla in Chile, known as the Hamburg/European Southern Observatory Survey, covers the southern hemisphere sky not visible from Spain. The plates are digitised and the data used all over the world (in the near future, the data will be put onto the internet for all to download). The plates are also extensively used for stellar work, for example to find extremely metal deficient stars or hot stars, such as white dwarfs and subdwarfs. A major effort was also the identification of X-ray sources from the ROSAT All-Sky Survey, a German X-ray satellite.

Fig. 17. The crucial PDS scanning machine, workhorse of the Hamburg Quasar Survey. Source: Hamburger Sternwarte

 

Fig. 18. Discovery plate of the quasar HS 1239+4633 with a redshift z=2.75. The image shows objective-prism spectra in a 5x5 arcminute field. The weak spectrum in the center corresponds to the quasar. A strong hydrogen emission line is easily visible as black dot superposed on the spectrum. Source: Hamburger Sternwarte

A new Stellar Astrophysics group was formed in 1998 by Professor Jürgen Schmitt. The work of this group includes a very large project for the future: the analysis of sun-like stars and a robotic telescope which will be built for installation in Tenerife. Called STELLA, this will be a 1 – 2m class telescope, controlled entirely robotically.

Fig. 19. STELLA (STELLar Activity): The new 1.2m robotic telescope to be operated on Tenerife by to study stellar activity. Source: Hamburger Sternwarte

A good indicator of the activity of the institute is the number of graduate students and PostDocs working in Bergedorf. These people are usually paid for several years by grants from official and private institutions supporting science. Applications for these grants must be made by the permanent staff, and are approved by an independent committee. Figure X shows clearly that the activity of the institute increased steadily in the eighties reflecting the shift of the observatory to extragalactic astronomy. In the nineties the number of third party staff levelled off at around 15.

Fig. 20. Number of third party staff working at Hamburg Observatory 1969 – 2000.22

5.2 Teaching

Astronomy lectures can be traced back until the 17th century, which were given by mathematicians and physicists interested in astronomy. Since the foundation of the University of Hamburg in 1919 the director of the Observatory had the right to give astronomy courses and lab exercises. It was also possible to make a doctorate award in astronomy given by the faculty of natural sciences. With the integration of the Observatory into the University teaching became mandatory for observatory staff and the lecture courses broadened and were integrated into the physics courses. From then on students took their diploma and doctorate awards in physics, with a focus on astronomy.25

Since 1968, Bergedorf has given lecture courses in astronomy for the physics department of the University of Hamburg. Bergedorf’s offerings in the realm of astronomical education are one of the attractive points of the university’s physics courses, helping to attract students from around Germany. Courses range from foundation courses, with lab exercises being carried out at Bergedorf itself, to specialised courses leading to diploma and doctorate awards. Typically six diplomas and doctorates are awarded each year.

In 1982, Weigert and Wendker published a foundation course in astronomy (Astronomie und Astrophysik. Ein Grundkurs. Latest edition Wiley-VCH Verlag, 2001) which is still used in courses at the University.

5.3 Working Conditions

Despite the variety of work carried out at the observatory, the difficulties of funding is a concurrent theme in the history of Bergedorf. In 1968, a memorandum was written to the authorities explaining the urgent need for more working space and better facilities, notably the requirement for a separate lab building. It was not however until nearly 10 years’ later that the lab building was completed, and even then various planned features were dropped to cut costs.22

The observatory has always depended to a certain extent on donations. For example, in 1969 a grant form the Volkswagen Foundation was obtained which resulted in the 1972 delivery of a Gitterspectrograph, and the Oskar-Lähning 1.2m telescope was the result of a donation.  In 1975, the observatory reported that owing to cost cutting, its personnel budget between 1975 and 1977 would be cut 11%, and in 1976 a sick librarian was not replaced, with the result that some books were lost.22

The first use of computing power at the observatory was in 1958 as already noted. Gradually the influence of computers on the work of the observatory increased: in 1974, a TR440 terminal was installed, linking the observatory to Hamburg University computing facilities, proving extremely valuable.22 More and more electronic devices were installed – in 1982, for example, the Great Refractor received a digital display, and in 1985 software was developed for the PDS scanning machine allowing for the first time detection of quasars on the Hamburg Quasar Survey plates semi-automatically (previously, the survey’s plates had been scanned by eye in the search for quasars!).22 In 1996 came the first mention of CCD devices in the annual reports (the basis of modern digital cameras, allowing digital analysis and manipulation of images), and in 1992 the observatory received its first parallel computing device.22 Of course, computers are not invincible: an electrical surge in 1988 caused serious damage to various electronic devices at the observatory.22

Good relations with local authorities have been a strength of the observatory, and this enabled Bergedorf to reach an agreement in 1984 with neighbouring Wentorf district to use yellow street lighting to reduce sky brightness.22 Such an agreement was reached with the local Bergedorf authorities some time ago.

5.3 Public outreach activities

Bergedorf has for some time been involved in public outreach activities of one form or another. Up to 1999, tours were offered to the general public during daytime and specialised tours for school classes and organised groups were arranged. Twice a year, weather permitting, the telescopes were open to the public for a week. After 1999, the observatory introduced monthly open evenings, including talks about current astronomical issues, and viewings through the telescopes. Annual numbers attending these events have remained static with a slight increase in recent years, but are nonetheless impressive (see Figure 21).

Fig. 21. Annual Number of Visitors to Hamburg Bergedorf Observatory Open Days 1990 - 2000.22

Special open days are held every few years at weekends. Each group in the observatory presents their work in the form of posters and the telescope buildings are opened for all to see. These open days are advertised locally and typically attract around 1000 visitors. In 1998, a special exhibition entitled Sterne Über Hamburg [Stars Over Hamburg] was held in a commercial centre in Bergedorf town in collaboration with a local historical society, detailing the history of astronomy in Hamburg. This event attracted over 2000 visitors.

In recent years there have been discussions about moving the observatory elsewhere, and using the site and its instruments for perhaps commercial purposes. The Förderverein Hamburger Sternwarte [Promotional Union of Hamburg Observatory – translation is the author’s] was formed in 1998 with 90 members, to both promote and protect the heritage of Bergedorf, its site and historical instruments, to enhance the visibility of the observatory and astronomy amongst the local population, and to engage the public.18 Some of the group’s activities can be found on the internet.26 This recently active group represents the most positive step towards greater public understanding of the observatory and its work.

Major astronomical events such as the appearance of bright comets (e.g. comets Kohoutek in 1973, Halley in 1986, Hale-Bopp in 1995 and Hyakutake in 1996), and solar eclipses such as the one of August 1999 cause a surge in public interest, often bringing several hundred people to the observatory and causing some significant extra work staffing the telescopes.22

            Fig. 22. Comet Kohoutek in 1974. Source: Hamburger Sternwarte

As an additional motivation for local youngsters to study physics, pupils in the last three years of their school studies (aged 16 – 18 years) are offered the opportunity to visit the observatory to gain practical experience of how astronomy and physics is actually carried out in a working environment. This programme (offered since 1999) is undertaken by around 60 pupils per year.

Recently the observatory become involved in a local schools project, the so-called Seh Stern [“See Star” - translation is SRA's] project.27 This is driven by a former Bergedorf astronomer, Dr Ulf Borgeest, in conjunction with the local authority for youth and vocational training. Bergedorf has provided support, and the project aims to provide opportunities for youngsters in local schools to become involved in astronomy at a young age, and has since September 2000 the Lippert telescope with a CCD camera at its disposal. With the shift of the Lippert dome into the responsibility of Seh-Stern and perhaps with the modernisation of the Oskar-Lühning telescope, a new focus for professional-amateur collaboration may emerge.  

Fig. 23. An experiment during the 2002 astronomy course for local pupils. Source: Hamburger Sternwarte

Fig. 24. Bergedorf Observatory in 1983. Source: Hamburger Sternwarte

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