How the Krasnopresnenskaya Observatory’s Seven-Inch Refractor Was Restored

The telescope at Krasnopresnenskaya Observatory is a seven-inch refractor that operated from 1903, helping astronomers at Moscow University study variable stars. The instrument was later dismantled, then reassembled in the 21st century from rediscovered historic components. According to the Sternberg Astronomical Institute of Moscow State University (SAI), only two parts had to be made anew: an equatorial wedge and one component of the mount’s rotation mechanism. By 2022, the instrument had returned to the Nazarov Tower in working order.

The reason for dismantling the refractor and the exact date remain unknown: SAI staff suggest it may have been in 1941 or later. The construction of the Nazarov Tower, the instrument’s scientific work and its restoration must be traced through various sources: the institute’s publications, research by museum historian Yuly Mentsin and accounts from those involved in the restoration.

Why did the observatory need a seven-inch refractor?

The new telescope was part of a programme to find and study variable stars: astronomers needed both to photograph the sky and to observe the objects they discovered. SAI explicitly links the purchase of the refractor to the start of this work at the university observatory. The instrument’s purpose is therefore easier to understand alongside another instrument used in Presnya: the photographic ‘equatorial camera’.

The astrograph was built in Dresden by instrument maker Gustav Heyde to sketches and technical specifications supplied by the observatory’s director, Vitold Tserasky. Sergei Blazhko took most of the astronomical negatives with it, while Lidiya Tseraskaya studied the images and discovered variable stars. The seven-inch refractor was intended primarily for their subsequent study. Photographic searches came before observations of objects already identified.

The refractor was ordered for the university observatory during Tserasky’s directorship. Heyde made the mount; funding came from the Moscow philanthropist Alexander Nazarov, who also paid for the construction of the small masonry tower. The objective lens was purchased from Carl Zeiss in Jena. SAI’s description gives its specifications: a diameter of 180 millimetres and a focal length of 3250 millimetres. The term ‘seven-inch’ refers to the size of the objective lens, rather than the length of the entire tube.

Those involved in the university’s work extended beyond the people who commissioned and built the instrument. SAI names Vitold Tserasky, Sergei Blazhko and Lidiya Tseraskaya among the founders of its school of variable-star research. Each of their lives encompassed more than the history of a single telescope, but this combination of observer, photographic material and analysis explains why a relatively small refractor was a scientific instrument as well as an ornament to the tower. SAI also reports that it was later used for other observations, but the museum article gives no programmes, dates or names of participants. It therefore provides no basis for attributing any specific result to the instrument beyond the study of variable stars.

How did observing a variable star complement photographic searches?

Comparing photographs could reveal an object whose brightness varied, but understanding the star’s behaviour required observations at different times. The university’s programme thus combined astronomical negatives, their analysis and observations with the refractor. This explains the general working principle; SAI’s article about the instrument includes no observing log with dates and the names of stars studied, so no specific discovery can be attributed to it.

A variable star is an object whose brightness changes measurably. The American Association of Variable Star Observers distinguishes, for example, between a star’s own pulsation and the eclipse of one star by another. These mechanisms produce different changes in brightness, which can be identified through a series of measurements. For repeated observations in Presnya, accurate pointing at the chosen star and ease of working with coordinates were important.

A photographic plate recorded a patch of sky as it appeared at the time of exposure. By comparing photographs, a researcher could spot an object whose brightness had changed; its subsequent behaviour then needed to be investigated. SAI’s account assigns specific roles: Sergei Blazhko took most of the astronomical negatives, Lidiya Tseraskaya analysed them, and the new refractor was used primarily to observe and study variable stars. This division of tasks does not establish that these roles were exclusive: the source provides no complete account of each participant’s working schedule.

Moscow’s ‘glass library’ began to take shape in the mid-1890s. An essay by Yuly Mentsin states that SAI holds several tens of thousands of glass negatives of the Northern Hemisphere’s starry sky; in 2019, he reported on work to digitise the collection. This is an image archive, rather than a photographic album of the seven-inch refractor itself. The distinction matters: the plates show the research programme’s longevity, but do not in themselves establish which components make up the restored telescope.

The astronomers’ work extended beyond a single instrument. According to an essay by Yuly Mentsin, head of the SAI museum, a Central Commission for the Study of Variable Stars was established at the institute and the Academy of Sciences in 1932, and in 1946 the International Astronomical Union entrusted the compilation of the General Catalogue of Variable Stars to scientists at SAI and the Astronomical Council of the USSR Academy of Sciences. Its compilation was the work of a team and subsequent generations, notably Boris Kukarkin and Pavel Parenago; it cannot be regarded as the achievement of a single telescope. Yet it is this early combination of photography and repeated observations that explains why an instrument from the early 20th century has retained its historical value.

When was the Nazarov Tower built, and when did the telescope begin operating?

The structure predates the earliest documented work with the refractor. According to research by Yuly Mentsin, head of the observatory’s history museum, in the summer of 1895 the walls of the Nazarov Tower and a pier for the seven-inch telescope were erected in the centre of the courtyard. SAI dates the start of the refractor’s operation to 1903. These dates refer to different events and should not be combined into a single ‘date of the telescope’s construction’.

The tower had its own construction timeline. In September 1895, Heyde’s firm supplied a five-metre dome, which was installed in October under the supervision of the university’s instrument maker, Vladimir Chibisov. In the summer of 1896, parquet flooring was laid in the tower, a partition was built on the ground floor and the walls were finished. The dome was painted with waterproof grey aluminium paint; the museum account shows that a separate support was being prepared for the telescope beneath the rotating structure.

The Nazarov Tower is part of an older university complex in Presnya, whose construction began following a donation by the merchant Zoy Zosima in 1827. The first observations at the observatory were recorded on 11 December 1831, according to ‘The Chronicle of Moscow University’. The small tower was built during the modernisation of the late 19th century, when Tserasky was director. Distinguishing these periods helps avoid associating the refractor with the observatory’s original building.

The complex’s main tower housed a different instrument: a 15-inch astrograph installed in 1900. It often appears in historical and contemporary photographs of the observatory, so an image of the large dome alone is no basis for concluding that it shows the seven-inch refractor. The latter belongs to the separate Nazarov Tower in the courtyard. The distinction between the two buildings and the instruments’ purposes explains the observatory’s layout at the turn of the century more precisely than the general phrase ‘the old telescope in Presnya’.

Which design features helped astronomers make observations?

SAI highlights two design features of the refractor: the position of the declination axis and the accessible location of the hour circle. The distance from the objective lens to the declination axis was two-thirds of the tube’s length, making the eyepiece end relatively short. This description concerns a specific historical instrument; without drawings and measurements of another telescope, it offers no basis for concluding that this arrangement is generally superior.

The mount’s polar axis was extended downwards. The hour circle sat at its lower end, allowing the observer to read coordinates without a bench or stepladder. SAI staff emphasise how convenient this arrangement was during hours of work. This detail helps explain scientific practice: the scale’s position determined how many extra movements an observer had to make.

It is useful here to distinguish between the telescope’s optical and mechanical components. The objective lens collects light; the mount supports and rotates the tube, allowing it to be aimed and used with coordinates. During restoration, the optics were found and put back in order, while two missing parts were made for the rotating support. Describing the work as ‘restoring an old tube’ therefore understates what was done.

Which documents help distinguish the stages in the instrument’s history?

The main sources for reconstructing this history are the museum’s description of the refractor itself, material on the observatory’s rebuilding and surviving images. They answer different questions. SAI’s account records the instrument’s scientific purpose and the outcome of its restoration; Yuly Mentsin’s research clarifies the construction of the Nazarov Tower; photographs help us visualise the buildings and individual stages of the work, but cannot replace a complete inventory of the telescope’s components.

The historian worked with an album of photographs of the rebuilding preserved in the observatory museum. The photographs and their captions were made by Sergei Blazhko, a participant in the scientific programme that later used the refractor. As Mentsin notes, the caption to one photograph of the building crew mentions a foreman working for the architect Konstantin Bykovsky. This inscription confirms a connection between the work and the university architect’s circle, but does not in itself prove that Bykovsky personally drew up the plans for every building and tower.

Mentsin’s article also notes a discrepancy with accounts that dated the reconstruction to 1905–1906. The documentary sequence he presents begins in the summer of 1895: first the north wing and the small tower, followed by work on the main dome and the meridian hall. This is a significant correction for anyone tracing the refractor’s history. Accepting the later date for the entire reconstruction without checking could easily lead to the mistaken conclusion that the Nazarov Tower was built after the telescope entered service in 1903.

A separate piece of evidence survives concerning the dome’s supplier. Mentsin describes a letter from Gustav Heyde to Tserasky, whose company letterhead featured a photograph of the Nazarov Tower. This source does not, however, establish which optical components have survived to the present day. A later account by staff at the Sternberg Astronomical Institute who worked directly with the museum object is more relevant to establishing the authenticity of the recovered objective lens.

This examination of the sources keeps three dates in their proper places: the tower was built in 1895–1896, the refractor was in use from 1903, and the restored instrument was ready for observations again by 2022. There are gaps between these dates for which no documentation is available. The publications neither reveal the exact delivery date of each component of the refractor nor provide a full record of its dismantling; these missing details cannot be replaced with an appealing, seamless narrative.

Why was the refractor dismantled, and what is known about when this happened?

The exact date and reason for dismantling are not established in the Sternberg Astronomical Institute’s published account. Staff suggest that the seven-inch refractor may have been dismantled during preparations to evacuate the institute in 1941, or later. They explicitly state that the details have yet to be clarified. This tentative explanation must not be turned into a claim about a specific day, order or person responsible.

What is known is that the instrument remained dismantled on the observatory grounds for several decades. This distinguishes its fate from a simple story of a lost exhibit. Individual parts had been preserved, but they needed to be found, matched to one another and returned to working order. A long period of storage separates its dismantling from the start of restoration, and the main published source does not provide a detailed sequence of where each part was moved during that time.

The institutional context also calls for precision. The P. K. Sternberg State Astronomical Institute was established in 1931 and was based at the Krasnopresnenskaya Observatory until its move to Leninskiye Gory. The Chronicle of Moscow University gives this period as 1931–1956. Dismantling the telescope therefore did not mean the disappearance of the entire observatory: the buildings survived and the complex’s history as a museum continued, even though the instrument did not fulfil its former purpose for many years.

What happened to the observatory while the telescope was stored dismantled?

The buildings in Presnya remained standing and took on new roles after the seven-inch refractor had been dismantled. The story of the site’s preservation explains how restorers in the 21st century were able to search for its parts on the original grounds at all. After the Sternberg Astronomical Institute was established in 1931, the observatory remained a research base for the institute; its departments moved to Leninskiye Gory during the 1950s, but the complex itself survived the move.

The sources give different milestones in this chronology. In his study of the observatory’s modernisation, Mentsin dates the Sternberg Astronomical Institute’s move to 1953; his later article with Konstantin Postnov places it in 1954. A history of Moscow State University’s Astronomy Division dates the completion of the new building and the start of the departments’ relocation to 1954, while the Chronicle of Moscow University records the institute’s presence in Presnya from 1931 to 1956. These publications probably describe different stages of the process; none of these dates establishes when the refractor was dismantled.

In the late 1970s, the future of the entire complex was uncertain. Mentsin writes of plans for demolition and protests from the astronomical community. In 1979 the buildings of the Krasnopresnenskaya Observatory were placed under state protection. The historian describes the complex as a monument of history and architecture, while the Chronicle of Moscow University calls it a monument of architecture and urban planning; neither publication reproduces the decision itself. The protection of the buildings and the expert council’s recognition of the seven-inch refractor in 2022 concern different objects.

The Museum of the History of the University Observatory and the Sternberg Astronomical Institute, founded at the initiative of astronomer Pyotr Kulikovsky around the turn of the 1960s, was originally based at Leninskiye Gory. According to the published study by Mentsin and Postnov, it moved into the main building in Presnya in 1981. The museum collected and preserved records and objects documenting the work of the university’s astronomers; the main building underwent restoration on a scholarly basis later, from the second half of the 1980s to the early 1990s.

These developments should not be confused with the restoration of the small telescope. The main building, the museum collection and the Nazarov Tower each had their own histories of repair and preservation. The Sternberg Astronomical Institute dates the start of dedicated work on the seven-inch refractor to 2008. The preservation of the grounds and the institute’s continued presence made the search possible in practical terms: the instrument’s parts were still at the observatory.

How were the historic components found and restored?

Restoration of the Krasnopresnenskaya Observatory’s 7-inch refractor began in 2008 with the involvement of active members of the Interregional Public Organisation ‘Astronomical and Geodetic Society’. The Sternberg Astronomical Institute’s account names I. T. Zotkin and F. V. Gorbunov as the project leaders. Finding the full set of components took time: several years were spent locating the historic parts and putting them in order. By 2022, the refractor had been reinstalled in its original position in the Nazarov Tower and restored to working order.

What survives of the early 20th-century instrument?

According to the final account by staff at the Sternberg Astronomical Institute, the restorers found almost all of the seven-inch refractor’s ‘original’ parts, including the objective lens made by Zeiss. The published report specifically identifies this surviving optical assembly and two newly manufactured mechanical parts; it does not list the other original components individually.

What is known about the restored refractor’s components from the account by Moscow State University’s Sternberg Astronomical Institute

Instrument component	What the source reports
Objective lens	The historic objective lens was found and put in order; its diameter is 180 millimetres and its focal length is 3250 millimetres.
Other original parts	Almost all were found, but the report does not specify their individual names, number or the proportion preserved.
Equatorial wedge	Newly manufactured during restoration.
Component of the mount’s rotation mechanism	One component was newly manufactured; its precise name is not given in the final account.

The phrase ‘almost all’ indicates that a large proportion has survived, but it is not a measured percentage. It cannot be used to calculate the number of original parts or to claim that a particular gear, fastener or eyepiece was made when the instrument was ordered. Equally, the two new parts do not make the telescope a replica: museum staff explicitly report that the historic objective lens and most of the original components were recovered and reinstalled.

Work on the Nazarov Tower needs to be considered separately. It was built for the telescope, and its platform and dome were refurbished during restoration, as participants described in a 2018 feature. The building, however, is not part of the mount. The statement that ‘only two parts were newly manufactured’ therefore refers to the refractor’s components in the Sternberg Astronomical Institute’s final report; it does not cover all repairs to the tower or mean that every recovered part was left without cleaning or refurbishment.

What did contemporary accounts reveal about the restoration while it was still under way?

A 2018 feature recorded an intermediate stage of the project: the telescope in the Nazarov Tower was already being assembled from recovered parts, but work was still under way. Journalist Natalya Steinert spoke to Fidel Gorbunov, who was involved in the restoration. In the article, he estimated that work on the refractor was around 90 per cent complete and discussed the dome’s rotation and testing its shutter mechanism separately. These remarks relate specifically to 2018; the final condition should be established from the Sternberg Astronomical Institute’s 2022 account.

According to Gorbunov’s account in the same feature, members of the Astronomical and Geodetic Society searched for parts on the institute’s grounds, found them in an old shed near the Nazarov Tower and consulted surviving photographs of the instrument. This eyewitness account sheds light on the practical aspects of the search, which the brief official report describes only in general terms. It does not replace an inventory, and the newspaper article cannot establish whether each recovered part was original.

The report mentions additional counterweights, the restoration of the observing platform steps and work on the dome. Gorbunov described the parts commissioned by those involved as a ‘drive arm made of high-strength bronze’ and an ‘authentic 19th-century cast-iron wedge’; the Sternberg Astronomical Institute (SAI) later listed an equatorial wedge and a component of the mount’s rotation mechanism as newly made parts. The descriptions use different terminology, and no published documents allow them to be matched precisely. The final list of new parts should follow the SAI account, excluding the counterweights and work on the tower.

The reporter recorded a female staff member’s recollection that the telescope may have been dismantled before the war or shortly afterwards because of damage to the floor. Gorbunov himself presents this as someone else’s recollection, rather than as a dismantling order he had found. A later SAI publication uses another cautious formulation: preparations for evacuation in 1941, or at a later date; the details are unknown. Until the reason is supported by documentary evidence, both accounts remain possible explanations rather than competing established facts.

Comparing the publications from 2018 and 2022 supports a reliable conclusion without inventing a dramatic narrative: the restorers progressed from a structure that was already partly assembled and undergoing checks to a working instrument in the Nazarov Tower, which was used for a demonstration observation of an eclipse. The available sources do not allow every operation carried out between those dates to be reconstructed precisely.

What did the eclipse observation in October 2022 demonstrate?

SAI reports that the restored seven-inch refractor was used for a demonstration observation of a partial solar eclipse in October 2022: the instrument was working again. Without such a test, an assembled telescope tube would have remained primarily a museum exhibit; a working instrument allows visitors to see how it operates in its original setting.

However, the publication provides no measurement logs, assessment of optical quality after restoration, pointing accuracy or list of subsequent regular observations. The demonstration does not establish that the refractor returned to the variable-star programme of the early 20th century or that its research capabilities are comparable to those of modern equipment. The conclusion is limited to an established fact: the restorers returned the telescope to working order, while the extent of its renewed scientific use remains unknown from the available material.

The eclipse demonstration took place in October 2022, and the expert council decided on the instrument’s status in December. This sequence matters: the certificate is not the only evidence that the instrument works, just as a single observation cannot replace a museum assessment of its provenance and state of preservation. These two reports answer different questions: whether the instrument works after reassembly, and whether its historical value has been recognised.

What does the instrument’s museum status confirm?

In December 2022 An expert council representing the museum community awarded the seven-inch refractor Category One ‘Monument of Science and Technology’ status under the ‘Monuments of Science and Technology of Russia’ programme. The Krasnopresnenskaya Observatory Museum received the corresponding certificate. This dated decision concerns the assessment of a specific museum object; it does not replace the history of its scientific use, which SAI presents separately.

The refractor’s value rests on several verifiable facts. Its mount was made to Tserasky’s order, its objective lens was supplied by Zeiss, and its observations were associated with the work of the Moscow school of variable-star research. This optical assembly survived the dismantling and was returned to the instrument. Finally, the restored telescope took its place once again in the small tower funded by Nazarov. Each link connects the physical object to particular people, scientific practice and a specific building.

How does a museum assessment account for authenticity after restoration?

The ‘Monuments of Science and Technology of Russia’ programme assesses a historical object against several criteria, including its date, scientific significance, associations with people and state of preservation. The Polytechnic Museum’s methodological guidelines address restored objects separately. Consequently, replacing a missing part does not in itself prevent an instrument from receiving museum recognition.

The methodology defines ‘state of preservation’ as an indicator of the degree of authenticity. A complete object that has been professionally restored is assessed differently from one that has never been repaired, but it remains eligible for assessment. The methodology awards 15 points for full preservation and completeness without restoration, and 5 points for full preservation and completeness after restoration. This comparison shows that restoration is considered separately from an object’s age and scientific significance. For the seven-inch refractor, SAI reports that almost all the historical parts were found, including the objective lens, and identifies two newly made parts. This is enough for readers to understand the basis of the museum’s decision; the available publication does not provide the instrument’s own score for each criterion, so it cannot be calculated from the general tables.

Under the methodology, the applicant submits photographs of the whole object, its markings and condition, an explanatory account of its creation and use, and an independent specialist’s opinion. Any missing information must be noted in the application. The status awarded to the refractor confirms the expert council’s decision, but SAI’s published report does not include the full documentation. It therefore does not reveal how the experts assessed the state of preservation of each assembly.

By that time, the Krasnopresnenskaya Observatory’s collection already included other recognised instruments. In their 2020 study, Mentsin and Postnov mention the 15-inch astrograph, Lydia Tseraskaya’s frame for finding variable stars and the astrophotometer designed by Vitold Tserasky as Category One monuments of science and technology. The seven-inch refractor received its status later. Ranking these objects by importance without a specific expert assessment is meaningless; together, they illustrate different stages of the work: photography, searching photographic plates, photometry and observation.

How does the history of a single telescope help us understand the observatory in Presnya?

The seven-inch refractor shows how commissioning scientific equipment, the work of observers and urban architecture came together at the university observatory. Under Tserasky, a separate tower was built, a photographic astrograph was used to search for variable stars, and the objects discovered were observed through this instrument. Decades later, institute staff and members of the astronomical society returned the surviving instrument to this sequence of work, restoring it to working order and distinguishing its historical parts from the new ones.

The Nazarov Tower is a physical reminder of this work, although it is impossible to see from outside which parts of the refractor survived its dismantling. SAI’s report on the recovered objective lens and the two new parts, together with the expert council’s decision in 2022, are important in assessing its authenticity. Together, these sources connect an early 20th-century scientific objective with the reassembled historical instrument.

The Krasnopresnenskaya Observatory is mentioned in the description Presnya tour provided by Radius Tour Bureau: the walk offers an exterior view of the setting of this story, but the itinerary does not promise entry to the tower or observations through the telescope. If you are interested in a private city walk, the bureau’s options are listed on the private tours page.

Sources

1. Sternberg Astronomical Institute, Moscow State University: The Krasnopresnenskaya Observatory’s 7-Inch Refracting Telescope
2. Yu. L. Mentsin: Architect Konstantin Bykovsky and the Modernisation of Moscow University’s Astronomical Observatory
3. Chronicle of Moscow University: Krasnopresnenskaya Observatory
4. Yu. L. Mentsin: Observing the Starry Sky from Krasnaya Presnya
5. Yu. L. Mentsin, K. A. Postnov: Moscow University’s Astronomical Observatory, 19th–21st Centuries
6. Polytechnic Museum: Guidelines for Identifying and Assessing Scientific and Technological Heritage
7. AAVSO: Variables — What Are They and Why Observe Them?
8. Natalya Steinert: Passionate About Their Sky, Moskovsky Komsomolets, 2018
9. Sternberg Astronomical Institute, Moscow State University: History of the Astronomy Department
10. Radius Tour Bureau: a tour of Presnya
11. Radius Tour Bureau: private tours of Moscow
12. Yu. L. Mentsin: Pavel Karlovich Sternberg and the Glass Plate Library of the Sternberg Astronomical Institute