History of the Astropeiler

The beginning of radio astronomy

More than 400 years have passed since Galileo Galilei first observed the stars with a telescope. In contrast, radio astronomy – as a branch of astronomy – is a fairly young science: 1933 saw the first reception of interstellar radio emissions. At the time, Karl Jansky was investigating interference in the transmission of radio waves and discovered, rather by coincidence, radio waves from the centre of our Milky Way.

Historischer Astropeiler

The first systematic search for radio radiation from space was carried out by radio amateur and communications engineer Grote Reber. In 1937, he built the first device that we, today, would consider a universal radio telescope in his garden; a parabolic reflector that could be tilted in all directions with a receiver at the focal point. The first complete sky survey was completed by him in 1943. However, only in the 1950s astronomers were able to interpret these observations correctly.

The beginning of the Stockert observatory

The decision to build the 25 meter telescope, which later became known colloquially as the “Astropeiler”, was made in the post-war years. On July 19th, 1955, the University of Bonn submitted the application for construction, and after the building permit was issued on November 22th, 1955, the Astropeiler was completed during 1956 and inaugurated on September 17th, 1956. Astronomical research began in 1957 with the study of line profiles of interstellar hydrogen.

In its time, the Stockert telescope was the most expensive science project in Germany. For a time, the 25 meter dish remained the largest telescope in Germany and remained the most precise radio astronomical device for several years.

A video collage (YouTube) shows impressions of the construction process, leading up to the inauguration.

Activities until 1975

In the 1960s, research continued in the 21cm wavelength range, i.e. observing emissions of interstellar hydrogen, supplemented by continuum measurements at 11cm. These were busy years at the obsevatory, and the activity soon made extensions necessary. Two residential buildings were built, one for operating staff and the other for scientists.

Plans for a laboratory building and second 10 meter telescope were made starting in 1963. The 10 m radio telescope was completed in August 1965, and the laboratory building was handed over at the beginning of 1966. Since the dish was designed for the observation of solar radio radiation and was also used in this way, it was called the “Sonnenspiegel” and the laboratory building was called the “Sonnenhaus”. The Sonnenhaus was extended by an annex in 1967.

In 1966 there was damage to the bearing of the 25-m dish, the telescope could then not be moved in azimuth for several months. After the repair, research shifted to continuum measurements in the 11cm range.

Experiences with the 25 meter telescope also went into the design of the new radio telescope in Effelsberg, and after its commissioning in 1972, research slowly began to migrate there. While in 1971 measurements were still being made continuously in the 21 cm range, the 25m telescope was only in limited operation in 1974/75 and was shut down by the Max Planck Institute for Radio Astronomy (MPIfR) in October of 1975.

Radioteleskope 1972

End of the seventies: Recommissioning

The Bonn University which had taken over the Astropeiler from the Max-Planck Institute started preparations for recommissioning in 1978. In July of 1979 things were ready to start a major measurement program, the “11-cm survey” of the galactic plane. This continued over 6 years all through 1985. During this time, the telescope was constantly maintained and improved. Reports mention major work on the steel structure of the antenna in 1983 and at the concrete of the building.

After completion of the survey further improvements of the 11-cm receiving chain were done and further observations in the wavelength range were performed. A former operator of the telescope has put a collection of photos from the eighties on his website. Also, an interesting story from the history of the observatory is told.

End of usage

Gradually it became more silent on the Stockert. The annual report of the universities Radio Astronomy Institute from 1990 hardly mentions the instrument. Actually, it was used for lab courses and diploma thesis. The last thesis was written in 1994 titled: 90 Tons brought to the Point and describes a new motion control program.

Starting all over

After the university withdrew from the Stockert in 1995, our association was founded and the telescope became a technical monument. The whole site was sold to a private company in 1997. During this time, amateur radio operators from our association started commissioning the 10-m dish for earth-moon-earth operation. When the new owner went into insolvency in 2004, fortunately the Astropeiler was aquired by the Northrhine-Westfalia Foundation. This foundation provided the funds for restoring the instrument.

In the second half of 2007 comprehensive anti-corrosion and restauration work was done. This was followed by work on the technical infrastructure including a complete replacement of the receiving systems. Also, the “Sonnenhaus” was completely renovated.

Staring in May of 2010 the site could be opened for visitors . Every Sunday both the historical technology as well as the new receiving and control system was shown.

In 2011, “second first light” was achieved which kicked off the radio astronomy observations, which we report here. Training and education of students as well as demonstrating radio astronomy to the general public is part of our efforts. The story of the old lady “Astropeiler” is still ongoing.

Today, Astropeiler Stockert is the largest and most capable radio telescope in the world operated by amateurs. Besides the Effelsberg telescope it is a particular astronomical landmark in the Eifel region.