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38-556: The original observing programme was the Sonneberg Field Patrol , which was begun in 1924 by Cuno Hoffmeister and ran until 1995. 41 fields of view along the northern Milky Way were photographed repeatedly at every opportunity. The instrument initially was a 170 mm/1200 mm Zeiss triplet lens . In 1935 a 400 mm/1600 mm quad-lens astrograph began operation, which was removed in 1945. In 1960 and 1961, two quad-lens astrographs were commissioned and

76-435: A discovery is Clyde Tombaugh 's discovery of the dwarf planet Pluto in 1930. Tombaugh was given the job of hunting for a suspected "9th planet" to be achieved by systematically photographing the area of the sky around the ecliptic . Tombaugh used Lowell Observatory 's 13-inch (330 mm) (3 lens element), f/5.3 refractor astrograph, which recorded images on 14-by-17-inch (360 mm × 430 mm) glass plates. In

114-504: A glass photographic plate or sometimes on photographic film . Many observatories of this period used an astrograph, beside instruments like the transit telescope , great refractors , and chronometers , or instruments for observing the Sun . Astrographs were often used to make surveys of the night sky , and one of the famous projects was Carte du Ciel . Discoveries using an astrograph include then-planet Pluto . Rather than looking through

152-501: A huge area of sky. Astrographs with higher f-ratios are used in more precise measurements. Many observatories of the world are equipped with the so-called normal astrographs with an aperture of around 13 inches (330 mm) and a focal length of 11 feet (3.4 m). The purpose of a "normal astrograph" is to create images where the scale of the image at the focal plane is a standard of approximately 60 arcsecs /mm. Astrographs used in astrometry record images that are then used to "map"

190-531: A quarter of all Galactic variables known. Two Cassegrain reflectors were used for photoelectric multi-colour measurements of variables. In the 1990s these were equipped with CCD cameras. There has also been an interest in meteors , meteorites and the zodiacal light . The museum has a meteorite collection on display. The observatory has a notable library, containing text books, monographs, conference proceedings etc., as well as periodicals and publications from other institutes and organisations. The library includes

228-473: A tradesman, Hoffmeister obtained his doctorate in 1927. During this time he had already started building what was to become Sonneberg Observatory. After his PhD, he moved back to Sonneberg and started expanding the observatory. Hoffmeister remained at the observatory until his death, even though the observatory lost most of its equipment after World War II and he was disowned as the observatory became part of East Germany's academy of sciences. Hoffmeister served as

266-457: Is a telescope designed for the sole purpose of astrophotography . Astrographs are mostly used in wide-field astronomical surveys of the sky and for detection of objects such as asteroids , meteors , and comets . Improvements in photography in the middle 19th century led to designs dedicated to astrophotography, and they were also popular in the 20th century. As in other photography, chemicals were used that respond to light, recorded on

304-456: Is designed to produce a particularly large (for example, 17 by 17 inches (430 mm × 430 mm)), flat, and distortionless image at the focal plane . They may even be designed to focus certain wavelengths of light to match the type of film they are designed to use (early astrographs were corrected to work in blue wavelengths to match photographic emulsions of the time). Wide-angle astrographs with short f-ratios are used for photographing

342-587: The Bibliographic Catalogue on Variable Stars , a card catalogue pinpointing literature up to the early 1990s on variable stars. This has been adopted and continued by the Centre de données astronomiques de Strasbourg . As of 1994, about 17,000 30 cm × 30 cm plates had been taken as part of the Field Patrol, about 131,000 13 cm × 13 cm plates as part of

380-469: The German Science and Humanities Council recommended closure of the site. Again, the director, now Woldemar Götz, managed to avert immediate closure. Instead, Sonneberg in 1992 became part of the state observatory Thüringer Landessternwarte Tautenburg ; it hence transferred from Brandenburg to Thuringia . Closure was now scheduled for 1993 with the plate archive to be moved to Tautenburg. In 1992

418-415: The 1950s three buildings with domes were added, which included laboratories and offices. In 1960 a new main building was erected, with basement and two floors. This has domes of 8 m and 5 m diameter. In 1962 the new survey station began operation, which could photograph the whole sky to −35° declination on a nightly basis with B as well as V filters. In the 1970s a separate workshop building

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456-535: The Astronomy Museum was set up, operated by the Freunde and a dedicated association Astronomiemuseum e.V. In 2000 the spin-off company 4pi Systeme – Gesellschaft für Astronomie und Informationstechnologie mbH (4pi Systems – Society for Astronomy and Information Technology Ltd) is formed by former staff of the observatory. It rents offices at the observatory and makes regular donations to

494-1016: The Astronomy Museum, is delegated to the Freunde. In 2007 the plate archive, library and instruments changed ownership from the state of Thuringia to the Zweckverband. These resources remain available to 4π Systeme to use and maintain them. As of 2008 there are 16 staff. Cuno Hoffmeister Cuno Hoffmeister (2 February 1892 – 2 January 1968) was a German astronomer , observer and discoverer of variable stars , comets and minor planets , and founder of Sonneberg Observatory . Born in Sonneberg in 1892 to Carl and Marie Hoffmeister, Cuno Hoffmeister obtained his first telescope in 1905 and became an avid amateur astronomer . After his father lost most of his money in 1914, Hoffmeister had to leave school in 1916 to start an apprenticeship in his father's company. During this time he continued to study spherical mathematics and trigonometry. In April 1915 he had

532-701: The Cassegrain reflectors. Children's birthdays and weddings can be held on site. The original 1925 building was small and had a 5 m dome. Several wooden barracks with movable roofs from that time no longer exist. The first building was later extended and then included a lecture hall. In 1938 a new instrument, an astrograph was installed. This was removed to the Soviet Union after the Second World War , but replaced in 1960/1961 with two astrographs, funded, resp., by Zeiss Jena and Hoffmeister. In

570-678: The Sky Patrol. The Schmidt camera added another 8500 13 cm × 13 cm plates. Another 5000 plates resulted from Hoffmeister's excursions to Latin America and Africa. As of 2008, the number of plates totals about 300,000. After that of the Harvard College Observatory , this is the second largest archive of astronomical plates worldwide. The archive is kept in two protected and climate-controlled rooms. The plate catalogue has been computerised. Digitisation of

608-438: The Zweckverband. By 2002 it became clear that the unique arrangement of a town and district running a research observatory was unsustainable in the long run. Since 2004 the observatory is run by 4pi Systeme on leasehold from the Zweckverband. 4π Systeme maintains the site and buildings, can use them commercially, continues the sky survey, and continues digitising the plate archive. Science outreach work, including operation of

646-414: The desired wavelength of light which is paired with the respective color-sensitive (black-and-white) photographic plate. In other cases a single telescope is used to make two exposures of the same part of the sky with different filters and color sensitive film used on each exposure. Two-color photography lets astronomers measure the color, as well as the brightness (magnitude), of each star imaged. Colors tell

684-400: The diameter and f-ratio of the objective , which determine the field of view and image scale on the photographic plate or CCD detector. The objective of an astrograph is usually not very large, on the order of 20 to 50 cm (8 to 20 in). The shape of the focal plane is often designed to work in conjunction with a specific shaped photographic plate or CCD detector. The objective

722-402: The director of the observatory until his death. During his life he played a leading role in supporting amateurs in observations of noctilucent clouds, aurorae, and nightglow. During his active life as an astronomer, Hoffmeister discovered approximately 10,000 variable stars on the more than 100,000 photographic plates taken at Sonneberg Observatory. The Minor Planet Center credits him with

760-501: The discovery of 5 asteroids between 1938 and 1963. He also co-discovered C/1959 O1 , a hyperbolic comet , in 1957. The lunar crater Hoffmeister and the two minor planets 1726 Hoffmeister and 4183 Cuno were named in his honor ( M.P.C. 3933 and 18307 ). Also Hoffmeister's star in Cassiopeia (V442 = Sonneberg 9484) and Hoffmeister's cloud at 20h47m/-42°. Astrograph An astrograph (or astrographic camera )

798-654: The observatory boomed. However, after the Berlin Wall was built in 1961, the Sonneberg Observatory found itself inside the restricted border area . In 1967 a reform of the academy resulted in the dismissal of Hoffmeister as director and the observatory becoming part of the Zentralinstitut für Astrophysik in Potsdam . The closure of the site was scheduled for 1969, research into variable stars

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836-582: The observatory suffered no direct damage. In July 1945 the area changed into the Soviet occupied zone . After the War, Hoffmeister was able to continue the research programme under Soviet occupation . However, the 400 mm astrograph and two survey cameras were removed to the Soviet Union as World War II reparations . At the same time, funding from Babelsberg ceased. Hoffmeister from his own savings, then

874-759: The observatory. He had been removed from his position as teacher in 1933 by the Nazi regime because of his membership in the Social Democratic Party of Germany . During the Second World War , from 1940 onwards, the observatory carried out weather observations for the Luftwaffe . Although the town was bombarded by the US Air Force in April 1945, just days before the area was occupied by the US Army ,

912-509: The observatory. The observatory did close at the end of 1994. Initiated by the Freunde, the town of Sonneberg and the district of Sonneberg formed the Zweckverband Sternwarte Sonneberg (Administration Union Sonneberg Observatory) in order to reopen the observatory in late 1995 with four staff and Constanze la Dous as director. Startup finance was secured from the states of Thuringia and Bavaria . In 1997

950-549: The opportunity to substitute as the assistant of Ernst Hartwig at Remeis Observatory in Bamberg while the current holder of the position was drafted, mainly working on observations of meteors and variable stars . He held this position until the end of the war and then moved back to Sonneberg, where he made his Abitur in 1920. After studying at the University of Jena , while at the same time continuing to work in his job as

988-402: The pair of images, using a device such as a blink comparator , astronomers are able to find objects that moved or changed brightness between the two exposures or simply appear in one image only, as in the case of a nova or meteor. Sometimes objects can even be found in one exposure since a fast moving object will appear as a "line" in a long exposure. One well-known case of an astrograph used in

1026-496: The plates began in the early 1980s. As of 2022, 85% of the plates had been digitised. Engaging the public in astronomy was an objective from the beginning as municipal observatory. The current Astronomy Museum opened in 1998 in the oldest building of the observatory. It is available for visits by individuals and groups. There are tours of the observatory and meteorite collection as well as weekly public observing sessions. It has at its disposal Hoffmeister's historic refractor and one of

1064-489: The positions of objects over a large area of the sky. These maps are then published in catalogs to be used in further study or to serve as reference points for deep-space imaging. Astrographs used for stellar classification sometimes consist of two identical telescopes on the same mount (a double astrograph). Each sky field can be simultaneously photographed in two colors (usually blue and yellow). Each telescope may have individually designed non-achromatic objectives to focus

1102-687: The present. The aim is to monitor not just particular fields, but the whole northern sky with repeat photography. Initially, four cameras were used, two at the Berlin Observatory at Berlin Babelsberg, where Guthnick was director, one at Bamberg and one at Sonneberg. In 1933 the Babelsberg cameras were moved to Sonneberg, in 1944 the one at Bamberg followed. The equipment was modernised in 1958 to consist of seven Zeiss Tessar 71 mm/250 mm lenses and seven Zeiss Tessar 55 mm/250 mm lenses. The fields of view are 26°×26°. Initially

1140-507: The star's "temperature". Knowing the color type and magnitudes lets astronomers determine the distance of a star. Sky fields that are photographed twice, decades apart in time, will reveal a nearby star's proper motion when measured against the background of distant stars or galaxies. By taking two exposures of the same section of the sky days or weeks apart, it is possible to find objects such as asteroids , meteors , comets , variable stars , novae , and even unknown planets . By comparing

1178-476: The support association Freunde der Sternwarte Sonneberg e.V. (Friends of Sonneberg Observatory) was formed by the observatory's acting director Hans-Jürgen Bräuer and the founder's nephew Klaus Hoffmeister. At the end of 1993, the staff level was down to 10. The 1994 IAU Symposium no. 161 held in Potsdam adopted a resolution emphasising the importance of the plate archive and calling on the authorities not to close

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1216-561: The survey was extended to 81 fields, which then included higher galactic latitudes . Both instruments had 400 mm aperture. Their focal lengths were 2000 mm and 1600 mm resp., resulting in fields of view of 8°×8° and 10°×10° resp. A 500 mm/700 mm/1720 mm Schmidt camera was used to monitor open star clusters . The second programme is the Sonneberg Sky Patrol . It goes back to an idea of Paul Guthnick 's, has been running since 1926, and continues to

1254-572: The telescope, it was discovered by using a blink comparator with images taken by an astrograph. By the late 20th century, electronic detectors became more common with the data being stored electronically. Most research telescopes in this class are refractors , although there are many (usually larger) reflecting designs such as the Ritchey-Chrétien and catadioptrics such as the Schmidt camera . The main parameters of an Astrograph are

1292-604: The town and the Carl-Zeiss-Stiftung, funded the observatory for a time. In April 1946 the Prussian Academy of Sciences was succeeded by the German Academy of Sciences at Berlin ; the observatory became a member institute. This led to an expansion in terms of buildings, and instruments; staff levels rose to 35. After Germany separated into East and West Germany in 1949, until the early 1960s,

1330-602: The town of Sonneberg and with support of the Carl-Zeiss-Stiftung . It worked in close collaboration with the observatory at Bamberg and Berlin Observatory at Berlin Babelsberg to monitor the sky photographically. In 1930/1931 the observatory transferred from the town to the state of Prussia and became formally affiliated to the Berlin Observatory. In 1938 Paul Ahnert took up a position at

1368-507: The whole sky down to −17.5° was covered, but in the late 1980s this was limited to −10° because of light pollution . The survey of the northern sky was augmented by plates taken on several excursions that took Hoffmeister to Bolivia , the Caribbean (1930 and 1933), South West Africa (1937/1938 and 1952/1953) and South Africa (1959). In the course of the photographic surveys, 11000 variable stars (as of 2009) were discovered,

1406-404: Was erected and all buildings were covered with aluminium sheet for insulation and protection against the elements. Since 1994 the site is listed as a historic monument . As of 2022, further restoration work is expected. There are currently the following telescopes and cameras: The observatory was founded in 1925 on the initiative of Cuno Hoffmeister as a municipal observatory financed by

1444-487: Was to end, staff was to move to Potsdam. The head of the observatory, Wolfgang Wenzel, managed to avert closure and then ignored a ban on using the large instruments until it was rescinded two years later. Until 1991 the observatory remained part of the Zentralinstitut; staff levels rose to 36. After German reunification in 1990 the observatory briefly came under the auspices of the state of Brandenburg . In 1991

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