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
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.
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
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