Pulkovo Observatory: Establishment and Observation

Pulkovo Observatory stands on the Pulkovo Heights south of St. Petersburg. In 1830, Friedrich Georg Wilhelm Struve explained to Nicholas I the inadequacies of the capital’s existing observatory instruments and the disadvantages of its city-center surroundings. The emperor supported building a new observatory outside the city. The Imperial Academy of Sciences subsequently formed a special committee chaired by Admiral Greig, with Struve helping to develop its scientific and instrumental plans.

The choice of site took account of foundations, sightlines, and surroundings. An initially proposed plot north of the city was constrained by its soil and proximity to urban areas. After comparing several locations, the committee chose Pulkovo. Tenant farmers’ houses and gardens already occupied the hill, and construction required their relocation, with resettlement elsewhere and compensation. Alexander Bryullov’s design was selected in 1834. Connections among observing rooms, studies, and living quarters were an important consideration in the building’s layout.

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The new observatory held its formal inauguration on August 19, 1839, or August 7 in the Russian calendar. The Academy attended as a body, and astronomers from Vilnius, Moscow, Kazan, Nikolaev, and elsewhere were invited. Struve became its first director, and the new institution served as Russia’s central observatory under the Academy’s direct administration.

Construction was not entirely complete at the time of the ceremony. Scientific observations had begun in 1839, but some supporting facilities and instrumental improvements continued through 1843. Struve’s detailed report, published in 1845, listed establishment costs of approximately 2.1 million paper rubles, covering buildings, instruments, roads, books, and publication of the report, but excluding the value of the allocated land. Sustained observation also depended on mechanics, assistants, and reliable operating funds.

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Pulkovo did not concentrate all its work on a single large telescope. A transit instrument made by Ertel measured stellar right ascensions, while a vertical circle was used for declinations and studies of refraction. A Repsold meridian circle measured stellar positions on a broader scale. There was also a prime-vertical transit instrument for investigating aberration and nutation. This division of work among instruments allowed some results to be checked against one another.

Struve traveled to Hamburg, Munich, and other places in 1834 to discuss drawings and operational details item by item with manufacturers. The large refractor built by Merz and Mahler had an effective aperture of approximately fifteen inches and was used to discover and measure double stars. During the ordering process, Struve also sought advice from colleagues including Bessel and Encke, bringing mechanical expertise together with specific observing requirements in the instruments’ design.

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The early program emphasized northern stars, extending observations south of the celestial equator to allow comparisons with other observatories. The report proposed a fundamental catalog of right ascensions and declinations for 362 bright stars, to provide reference points for wider measurements of stellar positions. Struve also reduced observations of seven stars near the zenith made between 1840 and 1842 for his investigation of aberration, publishing the results in 1843.

Improved precision involved repeated modifications to instruments. Observers’ body heat could disturb readings from spirit levels, so glass covers were installed. The meridian circle had originally required direct contact with the telescope tube or graduated circle to turn it; a separate operating mechanism was later introduced to reduce thermal and mechanical effects. The mechanic Pohrt and his assistants worked on modifications over an extended period. Delivery by the manufacturer was only the starting point in bringing a measurement system into use.

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During observations, astronomers first made pencil entries in bound notebooks, then transcribed them neatly into standardized registers and added instrumental corrections. The original manuscripts remained at the observatory for checking and recalculation. Regulations required the director to report the principal observations to the Academy annually and to send the annual publications to domestic universities, major observatories at home and abroad, and scholars participating in exchanges.

Publication lagged behind this plan. The 1845 report acknowledged that regular annual volumes had not yet appeared as required: arrangements for organizing them and the description of the observatory had to be completed first. A catalog of new double stars and two reports on chronometric expeditions had nevertheless been published separately. Early results thus circulated through several channels; continuous observing, calculation, and formal collected publication did not proceed in step.

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Pulkovo hosted young Russian and foreign scholars and trained officers of the General Staff and navy. Visitors took part in observations, reductions, and tasks requiring several people to work together. For the chronometric expedition of 1843, the Dorpat and Kharkov observatories lent timekeeping instruments; Schumacher helped assemble equipment, and Airy, director at Greenwich, supported the work. The central observatory’s cooperative network consisted of these concrete movements of equipment, people, and records.

The historian of astronomy Krisciunas attributes Pulkovo’s reputation to the precision of its measurements and their subsequent influence. He notes that accurate star catalogs required not only good instruments but also reduction parameters for precession, nutation, and aberration, together with analysis of systematic and random errors. When Newcomb synthesized these constants toward the end of the nineteenth century, he assigned substantial weight to some of Pulkovo’s results.

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