Category of Astronomical Heritage: tangible immovable
Brorfelde Observatory, Copenhagen University, Denmark

Description

Geographical position

Brorfelde Observatoriet, Copenhagen University, Gyldenkernes Vej 3-15, 4340 Tølløse, Brorfelde near Holb├ªk, Region Zealand, Denmark

Location

Latitude 55°37’29’’ N, Longitude 11°39’53’’ E, Elevation 60m above mean sea level.

IAU observatory code

054

Description of (scientific/cultural/natural) heritage

Copenhagen University Observatory (CUO) was established in 1642 on top of the famous Round Tower (Rundetårn) in Copenhagen.
It was moved to a new building at Østervoldgade in Copenhagen in 1861. In 1953, CUO was expanded with the Brorfelde Observatory.

Fig. 1. Brorfelde Observatoriet, located in Brorfelde near Holb├ªk, was founded in 1953 (CC3, Mogens Engelund, 2008)

Brorfelde Observatoriet, located in Brorfelde near Holb├ªk, 50km to the west of Copenhagen, was built between 1953 and 1964 by the University of Copenhagen in order to replace the Østervold Observatory in the center of Copenhagen. The main building, the workshop and the astronomers’ dwelling houses were designed by the Royal architect Kaj Gottlob (1887--1976). He was keen that the buildings should blend naturally into the beautiful landscape, and they were built of materials common to the area: yellow bricks and red tiles. He drew inspiration from the rural building style both for the main building itself and for the houses. The gardens and landscape were planned by landscape architect Georg E. Georgsen (1893--1976). The paving in the courtyard of the main building was done in a star pattern. (Wijngaard 2014).

Erik Høg started to work at the meridian circle from Aug. 1954 to approx. Oct. 1955 with the investigation of the stability of the instrument (Høg 2018, p. 442 ff).
With the Carlsberg Automatic Meridian Circle observations were carried out with a photographic micrometer in the years 1964-1976 and were published in four catalogues (Laustsen 1968, Fogh Olsen 1973, Fogh Olsen & Reimer 1977, Reimer & Fogh Olsen 1982). Between 1976 and 1981 the instrument was automated and equipped with the first ("prototype") photoelectric moving slit micrometer.
In 1979, the instrument was moved to the Roque de los Muchachos Observatory of the Instituto de Astrofisica de Canaria, on the island La Palma in the Canaries, where it started operation in 1984 in a collaborativ programme between Copenhagen University Observatory, Royal Greenwich Observatory and Real lnstituto y Observatorio de la Armada en San Fernando (Helmer et al. 1991).

Fig. 2a. Brorfelde Observatoriet (1953), (Efter Thykier: Dansk Astronomi i 400 Aar)

Fig. 2b. Brorfelde Observatory, Residential building, Observator Gyldenkernes Vej 13 (CC4, Ramblersen2)

Fig. 2c. Brorfelde Observatoriet, Workshop building (CC2, Jose Kniesek)

Fig. 2d. Brorfelde Observatoriet, Meridian building (Efter Thykier: Dansk Astronomi i 400 Aar)

Copenhagen University used the Brorfelde Observatory until 1996. The telescopes are still used by University of Copenhagen students, but the new Astronomical Institute with the entire scientific staff has moved to the Rockefeller Complex in Copenhagen.
Already in 1993, the Niels Bohr Institute was created by merging the Astronomical Observatory, the Ørsted Laboratory and the Geophysical Institute.

Finally in 2009 the buildings were put up for sale, because the running of the observatory became too expensive for the University.

History

Fig. 3a. Brorfelde Observatoriet, Schmidt telescope dome (pixabay)

Fig. 3b. 50/77-cm-Schmidt telescope of Brorfelde Observatory (CC3, Mogens Engelund)

Fig. 3c. Carlsberg Automatic Meridian Circle (CAMC), moved to La Palma in 1983/84 (credit: Erik Høg)

Instruments

50/77-cm-Schmidt telescope (focal lenth 150.35cm, focal ratio f/d = 1/3), built in the Brorfelde workshop (1966),
the mechanical control system was replaced by a computerised control system in 1980.
The Schmidt telescope is still active and the photographic glass plates was replaced by a modern CCD camera and field flattener.
7-inch transit circle
18-cm-Carlsberg Meridian Circle, made by Grubb & Parsons, Newcastle upon Tyne (1952), mounted in 1953,
donated by the Carlsberg Foundation, now known as the Carlsberg Automatic Meridian Circle (CAMC), moved to La Palma in 1983/84;
the first CAMC photoelectric micrometer was in use until February 1988,
a copy of this micrometer is being installed at the San Fernando meridian circle (Helmer et al. 1991).
In 1998, a fixed CCD detector allowed to track an entire strip of sky with ~100,000 much fainter stars;
15 large catalogues of accurate positions have been published.
The CAMC was decommissioned in 2013.

Automatic Photographic Plates Measuring Machine GALAXY
Horizontal Glass Meridian Circle (GMC), built in the Brorfelde workshop (1967),
proposed by Høg (1971), IAU Study Group for Horizontal Meridian Circles, 1973 to 1991, Erik Høg chairman.
Erik Høg visit in China 1980 and 1982. In 1981 Dr Hu Ningsheng, Director of the Nanjing Astronomical Instrument Factory (NAIF), visited Brorfelde.
The plan was for the Danish Chinese Meridian Telescope to be jointly developed and then built at the Nanjing factory
for installation at the observatory near Xian in Shanxi. The Danish Meridian Circle was moved to China in 1989.
36/20-cm-Double-Astrograph (36-cm-visual lens, focal length 4.9m, 20-cm-photographic lens, focal length of 4.8m), (1895) -
moved from Østervold Observatory
50-cm-Cassegrain (focal length of 6.8m), built in the Brorfelde workshop (1958--1969);
then it was installed at La Silla Observatory in Chile, where it was used until 1994.
Now it has been decommissioned and replaced with a modern amateur telescope
30-cm-Steinheil Refractor (f/10), which has now been replaced with a 250mm f/9 LZOS/APM triplet apochromat
1.54-m-Cassegrain Reflecting telescope, built in the Brorfelde workshop after 1967 for operation in La Silla Observatory, Chile.
Photoelectric photometers and photographic cameras were also built in the Brorfelde workshop.

A GIER electronic computer (Institute of Geodetics Electronic Calculator) - with all of 1k of memory!, the first modern computer at the University in in Copenhagen was acquired in 1962, funded by the Carlsberg Foundation (Petersen 2015).

Fig. 3d. Brorfelde Observatoriet, Meridian circle in 1954 (credit: Erik Høg)

Fig. 3e. Kjeld Gyldenkerne (1919--1999), (credit: cassiopeiabloggen, 2010)

Micrometer Development

"Photoelectric micrometers have a long history in meridian instrumentation, starting with Strömgren’s proposal in 1933 of a slit micrometer. But the early ideas had to await the advent of the photomultiplier, digital electronic equipment and of the digital computer before they could bear efficiently in practice." (Høg 1974).

"The traditional visual micrometer has had continuously growing competition from more accurate and efficient techniques since the 1960s. The methods include a photographic micrometer (Laustsen 1967), a photoelectric multi-slit micrometer (Høg 1972), a photoelectric tracking micrometer (Requilème 1973, Requilème & Mazurier 1986), an image dissector micrometer (Hughes et al. 1986) and plans for a CCD micrometer (Stone & Monet 1990)." (Helmer et al. 1991).

The photoelectric multi-slit micrometer for simultaneous observation of R.A. and Decl. designed by Erik Høg (1972) was completed at the Hamburg Observatory in 1967 and used for the Perth expedition. "The mean error at zenith was 0.18’’ in right ascension and 0.21’’ in declination. The micrometer had 21 pairs of fixed slits, each pair consisting of two mutually orthogonal slits inclined at 45° to the meridian. From the times when a star crosses the slits, the x,y coordinates of the star are derived." (Helmer et al. 1991).
"The experience gained with this Høg micrometer was the basis for the first photoelectric moving slit micrometer for the Carlsberg Automatic Meridian Circle (CAMC), basically designed by E. Høg, where one slit pair is moved across the image of the star several times during each transit. With this micrometer a zenith mean error of 0.19’’ and a limiting magnitude of 13^m was reached." (Helmer et al. 1991).

Corresponding successful developments of three different methods (with photographic and photoelectric micrometers) were started at the Brorfelde, Hamburg-Bergedorf, and Bordeaux observatories which have now given about 160,000 observations with an average mean error of 0.22''.

The use of a photoelectric star sensor or Star Tracker is the most direct way to replace the human eye in the impersonal Repsold micrometer. An account of the many different types of star sensors has been given by Kühne (1971, 1983), e.g. Rotating knife-edge like at the 19-cm-meridan circle at Bordeaux.

It carries good promise for 'the future that new meridian circles employing modern techniques are being put into operation at Caracas (CIDA, Merida), Venezuela, Sao Paolo, Brazil, and US Naval Observatory, Washington D.C., and one is planned for Mitaka Observatory, Tokyo. (Høg 1974).

In addition, in the 1960s, meridian astronomers started utilizing electronic computers as soon as they became available to relieve the meridian observer from the burden of routine tasks. Watts (1960) and Adams (1963) described the pioneering work at the US Naval Observatory, Washington D.C.. The introduction of quartz clocks and a digital chronograph at Royal Greenwich Observatory in Herstmonceux has been surveyed by Tucker (1963) (Høg 1974).

Fig. 3e. Erik Høg and Dr. Hu Ningsheng with the Glas Meridian Circle in Brorfelde, 1981 (Photo: Politiken)

Fig. 3f. Glas Meridian Circle model, Brorfelde, 1980 with the astronomers Nr. 1+3: L.V. Morrison and R.H. Tucker, UK, Nr. 2+6: J.L. Muiños and L: Quijano, Spain, Nr. 4+5: C. Fabricius and Erik Høg (credit: Claus Fabricius)

Modern meridian circles and two satellites, Hipparcos and Gaia, have revolutionized the positional astronomy, the new astrometry, for two billion stars.

Fig. 4a. Hipparcos Satellite (Photo: Erik Høg)

Fig. 4a. Gaia Satellite (Photo: Erik Høg)

Astronomers at Brorfelde, 1953 to 1996 (Move to Copenhagen)

Copenhagen University Observatory (CUO) with Østervold and Brorfelde Observatories had a single director.

Bengt Strömgren (1908--1987), director from 1940 to 1951, was the founder of Brorfelde Observatory.
He was succeeded as director by Anders Reiz (1915-┬¡2000) in 1958 (until 1972).

In the mid-1970s the Observatory had two professors, approx. 20 scientific staff, as many in workshops and offices, and many students. After the democratic evolution at the University about 1972 a number of astronomers took office as director, most of the time it was Professor Henning Elo Jørgensen (1938--2010), professor 1982 to 2005; director for several periods.

Julie Marie Vinter Hansen (1890--1960), daily leader of the Copenhagen and Brorfelde observatories in the years until 1958
Anders Reiz (1915-┬¡2000), director 1958 to 1972, professor 1958 to 1985
Henning Elo Jørgensen (1938--2010), professor 1982 to 2005; director for several periods
Erik Høg (*1932), 1953 to 1958, 1973 to 1980/2002,
construction of a photoelectric micrometer with photon counting, a further development of the one he had built in Hamburg.
Peter Naur (1928--2016), 1955 to 1959, development of electronics for the use of photographic technique at meridian circle,
Danish computer science pioneer and Turing award winner.
Svend Laustsen (*1927), observer with the photographic micrometer 1959 to 1968
Kjeld Gyldenkerne (1919--1999), 1957 to 1999
(Wijngaard 2014)
Vagn Mejdahl (1928--1997), observer 1959 to 1960
Gijsbert van Herk (1907--1999), observer 1961 to 1962
Hans Jørn Fogh Olsen (*1943), observer 1968 until 1979, discoverer of 4 minor planets
Leif Helmer (*1943), observer 1969, director from 1979 until 2004
Claus Fabricius (*1954), observer at meridian circle 1980 to 1994, development and move of the meridian circle to La Palma
(now University of Barcelona and Institute for Space Studies of Catalonia)
Johannes Andersen (1943--2020) and his wife, Birgitta Nordström, 1972 to 1996 (then to Copenhagen), visit in China 1986

Erik Høg and Leif Helmer worked together in 1974/76 on the publication of the catalogue of 25,000 stars from the Hamburg Meridian Observations in Australia. Leif Helmer developed the software for the La Palma meridian circle, so that the telescope could be operated remotely via the Internet. In 2005, Spain took over meridian circle on La Palma.
The Cook meridian circle from the Royal Greenwich Observatory in Herstmonceux was installed in the meridian circle dome in Brorfelde in the early 1990s and used in the testing of CCD micrometers for measuring the star and for reading the meridian circle before being sent to La Palma. It was later transferred to the National Maritime Museum in Greenwich. In 1996, the new micrometers were put into use on La Palma after being built in Brorfelde. They used CCD detectors instead of photon counting, so that far more and much fainter stars could now be observed with greater accuracy. (Høg 1922).

TAPs (Technical Administrative Personnel)

Poul Bechmann (1916--2000), manager of the workshop, 1955 to 1986
Ralph Florentin Nielsen (1940--1995), manager of the workshop
Knud Seifert Jensen, workshop
Hugo Hansen, technical assistant
Torben Knudsen
Bodil Jensen, observer at the meridian circle, 1964 to 1973
Poul B. Jensen, 1964 to 1973, discoverer of 98 minor planets, co-discoverer (with Carolyn S. Shoemaker) of the Comet Jensen-Shoemaker (1987g1).
Jensen worked for 35 years in the Meridian Circle Department and participated at the minor-planet program using the Schmidt telescope.
Karl A. Augustesen (*1945), co-discoverer of 6 numbered asteroids during 1984-1987

Discovered Asteroids

Minor Planet Center (MPC) of the International Astronomical Union (IAU), founded in 1947.
See also the list of 98 minor planets, discovered by Poul B. Jensen.

3033 Holbaek March 5, 1984
3309 Brorfelde January 28, 1982
3312 Pedersen September 24, 1984
3369 Freuchen October 18, 1985
5165 Videnom February 11, 1985
5427 Jensmartin May 13, 1986
(7743) 1986 JA May 2, 1986
8261 Ceciliejulie September 11, 1985
9555 Frejakocha April 2, 1986
(8338) 1985 FE3 March 27, 1985
(22282) 1985 RA September 11, 1985
(24642) 1984 SA September 22, 1984

The Hungaria asteroid 3309 Brorfelde was discovered at, and named for the observatory -- 1987 (M.P.C. 12210).

State of preservation

Fig. 4. Brorfelde Observatoriet at night (photo: Jonas Whitehorn, CC4, Brorfeldeobservatorium)

The buildings of Brorfelde Observatory and the hills, even the night sky (Mørkefredning "Dark site") above Brorfelde are now protected and have been handed over to Holb├ªk municipality. Brorfelde Observatory is in the Heritage Agency of Denmark database for Listed Buildings.
The road leading up to the observatory was named Observator Gyldenkernes Vej after the first influential director.

Comparison with related/similar sites

It is similar to Hoher List Observatory, Schalkenmehren, Eifel (1954--2012) as outstation of Bonn Observatory.

Threats or potential threats

no threats, it seems to be in good condition.

Present use

The telescopes of Brorfelde Observatory was used from 1996 to 2009 by University of Copenhagen students. Two amateur astronomical societies, the Brorfelde Circle of Friends and the Copenhagen Astronomical Society, also used the domes.

In 2009, Freja Ejendomme wanted to sale the area. But local people succeeded to protect the ensemble in 2012. Then in 2013, Holb├ªk Municipality bought the observatory. An experience centre is now developed that will focus on everything between heaven and earth: Or more precisely geology, nature and astronomy for school classes, families and others who want to experience and learn. (Bouchet & Olsen, 2014).

Astronomical relevance today

Fig. 4a. Brorfelde Observatory under the Milky Way (photo: Stanley Photography, CC4, Brorfeldeobservatorium)

Brorfelde Observatory was the University of Copenhagen observatory from 1953 to 1996. The emphasis of research was in asteroid discoveries with the help of the Schmidt telescope, and innovative astrometry with one of the best meridian circles in the world.

In 1996, the personel from Østervold and Brorfelde Observatories moved to "The Rockefeller Building" at Juliane Maries Vej in Copenhagen. In 2005, this 363 years old institution was merged with the "Niels Bohr Institute".

In addition, the astronomers have the 1.5-m-Danish Reflector at ESO, La Silla, Chile, for observing the Southern sky.

Fig. 4b. 1.5m-Danish-Reflecting telescope, ESO, La Silla, Chile (Erling Poulsen History)

References

Bibliography (books and published articles)

Andersen, Johannes: The Carlsberg Foundation and Danish Astronomy: A Century of Sustained Support. Historical Research Project (02/05/2016).
Bouchet, Julie K.L. & Mia B. Olsen: Brorfelde Observatorium åbner som oplevelsescenter. In: KVANT (december 2014), p. 15-17.
Carlsberg Meridian Catalogue, La Palma, No. 4 (1989), Copenhagen University Observatory, Royal Greenwich Observatory, Real Instituto y Observatorio de la Armada.
Fogh Olson, Hans Jørn; Jensen, Poul & T. Knudsen: Meridian observations made in Brorfelde (Copenhagen University Observatory) 1967--1969. Positions of 2246 stars brighter than 11. 0 vis. mag. In: Astronomy and Astrophysics Supplement 9 (1973), 1.
Gyldenkerne, Kjeld: Carlsbergmeridiankredsen og La Palma observatoriet. In: Fysisk tidsskrift 82 (1984), nr. 4, S. 145-154.
Gyldenkerne, Kjeld: Fyrre år i Brorfelde. [Forty years in Brorfelde] In: Astronomisk Tidsskrift (1986), no. 3, S. 97-119.
Gyldenkerne, Kjeld: Universitetsobservatoriet og dets forskning. In: Københavns Universitets almanak (1989), S. 101-117
Helmer, J.; Fabricius, C. & L.V. Morrison: The Micrometers of the Carlsberg Autumatic Meridian Circle. In: Experimental Astronomy, Vol. 2 (1991), p. 85-99.
Høg, Erik: Proposal for a Photoelectric Meridian Circle. In: Astronomische Abhandlungen der Hamburger Sternwarte V (1960), p. 263-272.
Høg, Erik: A theory of a photoelectric multislit micrometer. In: Astronomy & Astrophysics 4 (1970), p. 89-95.
Høg, Erik: A solution of the problems of flexure and refraction in fundamental astrometry. In: Mitteilungen der Astronomischen Gesellschaft 30 (1971), p. 148-151.
Høg, Erik: The photoelectric meridian circle of Bergedorf/Perth. In: Astronomy & Astrophysics 19 (1972), p. 27-40.
Høg, Erik: Design study of a glass meridian circle. In: Mitteilungen der Astronomischen Gesellschaft 32 (1973), p. 120-125.
Høg, Erik: Modern Developments of the Meridian Circle. In: Gliese, W.; Murray, C.A. & R.H. Tucker (eds): New Problems in Astrometry. International Astronomical Union / Union Astronomique Internationale, Vol. 61. Dordrecht: Springer 1974, p. 243-255.
https://doi.org/10.1007/978-94-010-2199-9_49
Høg, Erik; Von der Heide, Johann; Fischer-Treuenfeld, Friedrich von; Holst, Gerhard; Loibl, Bernd; Ziegler, Ulrich; Nikoloff, Ivan & Helmer Leif: Perth70. A catalogue of positions of 24,900 stars. Derived from Observations within the SRS-Program during the years 1967 through 1972 with the Hamburg Meridian Circle at Perth Observatory, Bickley, W.A. Hamburg (Abhandlungen aus der Hamburger Sternwarte; Band IX) 1976, p. 15-53 and 1-334.
Høg, Erik: Astrometry accuracy during the past 2000 years. in: Contribution to the History of Astrometry, No. 7 (2008),
http://adsabs.harvard.edu/abs/2011arXiv1104.4554H
Høg, Erik: Astrometry during the past 100 years (2011),
http://arXiv.org/abs/1105.0634
Høg, Erik: Astrometry 1960-1980: From Hamburg to Hipparcos. In: Wolfschmidt 2014, p. 84-153.
Høg, Erik: Young astronomer in Denmark 1946 to 1958. In: Wolfschmidt 2018, p. 418-453.
Høg, Erik: Om dansk astrometri efter Tycho Brahe. In: Kvant, Tidsskrift for Fysik og Astronomi (June 2022).
http://www.astro.ku.dk/~erik/xx/kv222-EH-Efter Tycho-online.pdf
Kühne, C. [Zeiss]: A new automatic meridian circle PMC 190. In: Astronomy & Astrophysics 121 (1983), p. 165-173.
Jensen, Poul; Augustesen, K. & E. Shoemaker: Comet Jensen-Shoemaker (1987g1). IAU Circular 4505 (1987), 1.
Jensen, Poul; Augustesen, K. & E. Shoemaker: Minor Planet Observations [054 Brorfelde]. In: Minor Planet Circular 50596 (2004), 2.
Jensen, Thomas of Bornholm: Personal communication (Nov. 24, 2022).
Laustsen, Svend: [Photographic micrometers in Brorfelde meridian circle]. In: Mat. Fys. Medd. Dan. Vid. Selsk. 3 (1967), no. 3.
Laustsen, Svend: Meridian Observations made in Brorfelde 1964-1967. In: Mat. Fys. Medd. Dan. Vid. Selsk. 3 (1968), no. 6.
Minor Planet Discoverers (by number). Minor Planet Center. MPC/MPO/MPS Archive. Retrieved Nov. 23, 2022.
Petersen, Jørgen Otzen: Observatoriet på Østervold i v├ªkstperioden 1958--1975, DASK og GIER - dengang og nu. In: KVANT (Mai 2015), p. 26-35.
Schmadel, Lutz D.: "(5171) Augustesen [2.42, 0.13, 7.1]". In: Dictionary of Minor Planet Names -- (5171) Augustesen, Addendum to Fifth Edition: 2003-2005. Berlin, Heidelberg: Springer 2006, p. 25 (doi:10.1007/978-3-540-34361-5_98)
Schmadel, Lutz D.: "(5900) Jensen". In: Dictionary of Minor Planet Names -- (5900) Jensen. Berlin, Heidelberg: Springer 2007, p. 496 (doi:10.1007/978-3-540-29925-7_5517).
Wijngaard, Marina: Om stjerner og stjernekiggere på Tølløse egnen ved Marina. In: Lokal Historisk Forening for Tølløse Egnen, Forår 2014 (Local Historical Association for the Tølløse Region, Spring 2014).
Wolfschmidt, Gudrun (Hg.): Kometen, Sterne, Galaxien - Astronomie in der Hamburger Sternwarte. Zum 100jährigen Jubiläum der Hamburger Sternwarte in Bergedorf. Proceedings of the conference held in Hamburg in 2012. Hamburg: tredition (Nuncius Hamburgensis; Band 24) 2014.
Wolfschmidt, Gudrun (Hg.): Astronomie im Ostseeraum. Astronomy in the Baltic. Proceedings der Tagung des Arbeitskreises Astronomiegeschichte in der Astronomischen Gesellschaft in Kiel 2015. Hamburg: tredition (Nuncius Hamburgensis; Band 38) 2018.