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Leiden University archives, Observatory, directorate H.G. van de Sande Bakhuyzen

Identifier: ubl145

Scope and Contents

The archive consists of professional correspondence, correspondence and papers regarding the management of the Observatory, and papers regarding the maintenance and performance of the scientific instruments of the Observatory. It also includes papers regarding the expedition to Réunion to observe the Venus transit of 1874 and a gigantic liber amicorum with photos of astronomers and other scientists, both from the Netherlands and other countries, that was presented to Van de Sande Bakhuyzen in 1908.


  • Creation: c. 1873-1923
  • Creation: Bulk c. 1873-1908


Language of Materials

Mostly Dutch, also German, French and English

Conditions Governing Use

Since the archive is digitized, the original papers are not free for public access, unless with permission of the curator after a written request with motivation. Other regulations that apply during the use of these materials can be found on the website of Leiden University Library.

Biographical / Historical

Hendricus Gerardus van de Sande Bakhuyzen (1838-1923) studied engineering before coming to Leiden to study astronomy. He first worked as a school teacher, and after that he was briefly professor of applied physics at the Delft Polytechnic before succeeding Frederik Kaiser as director of Leiden Observatory in 1872. His main scientific work regarded the elimination of systematic errors from astronomical observations (esp. fundamental astrometry), including errors of instruments and personal errors of the observers. He also worked on geodesy (measuring the earth). He was one of the organisers of the Venus transit expedition in 1874-1875, although he did not participate in the expedition himself.

Bakhuyzen was active in several international organisations, including the Astronomische Gesellschaft , the International Geodetic Association and the Carte du Ciel project, although Leiden did no contribute to the photographic Carte itself. Between 1888 and 1900 he was president of the Royal Academy of Sciences.

During his directorate, Leiden Observatory acquired a new 10-inch refractor and a 13-inch photographic refractor. Nevertheless, this period is often regarded as a period of decline. One frequent comment is that observations were published late, if at all.

At the occasion of his retirement in 1908, Bakhuyzen was given a monumental Album Amicorum, containing pictures of hundreds of scientists, both Dutch and foreign. He was succeeded by his brother and student E.F. (Ernst) van de Sande Bakhuyzen.


106 items (c. 1.05 metre)

Abstract in Dutch

Archief van H.G. van de Sande Bakhuyzen, hoogleraar sterrenkunde in Leiden en directeur van de Leidse Sterrewacht (1873-1908), bestaande uit wetenschappelijke en administratieve correspondentie en stukken betreffende de wetenschappelijke instrumenten van de nieuwe Leidse Sterrewacht. Tevens stukken betreffende de expeditie naar Réunion voor de waarneming van de Venusovergang van 1874 en een monumentaal liber amicorum met foto’s van astronomen en andere wetenschappers uit zowel Nederland als andere landen, in 1908 aan Van de Sande Bakhuyzen geschonken.

Abstract in English

Archive created by H.G. van de Sande Bakhuyzen, professor of astronomy at Leiden University and director of Leiden Observatory (1873-1908). This archive consists of professional and administrative correspondence, and papers regarding the scientific instruments of Leiden Observatory. It also contains the papers of the expedition to Réunion to observe the Venus transit of 1874 and a gigantic liber amicorum with photos of astronomers and other scientists, both from the Netherlands and other countries, that was presented to Van de Sande Bakhuyzen in 1908.


The inventory consists of the following categories:

Correspondence by correspondent (no. 1-29)
Correspondence by institution (no. 30-34)
Correspondence by subject (no. 35-42)
Notes and observations (no. 43-52) (including papers of the Venus transit expedition)
Observatory Management (no. 53-61)
Instruments (no. 62-105)
Liber amicorum

To facilitate researchers, each file has been given a short title. In some cases these titles were original designations by the authors. The other titles are given by the author of this inventory. The main subject of each file is indicated in the inventory. This is not an exhaustive description, but a first indication, intended for researchers.

Correspondence has been ordered alphabetically by correspondent, following the Dutch system (disregarding prefixes such as van, van der etc).

Within the files, correspondence has been ordered chronologically. Other papers are preserved in the order in which they were found.

"Correspondence with ..." indicates that the file contains letters from both correspondents; "letters from …" indicates that only one side of the correspondence has been preserved in this archive.

Physical Location

Leiden University Library, Special Collections

Custodial History

This archive was created by H.G. van de Sande Bakhuyzen in the course of his work. The papers were preserved in Leiden Observatory until they were transferred to Leiden University Library in 2010.

Some files come from the collections of Museum Boerhaave. These files are indicated in the inventory.

Over the years, several papers have been temporarily removed for research purposes or for exhibitions, for example the papers of the Venus transit expedition. These papers have been returned to the archive.

Immediate Source of Acquisition

The archive was transferred to Leiden University Library in 2010, by agreement between Leiden Observatory, the Leiden University Library and the Department of Documentary Information and Archive Administration of Leiden University.


No selection has been made in this archive.


No future additions are to be expected.

Existence and Location of Copies

The archive is digitized. The images are available through the inventory.

Related Materials

This archive is part of Leiden Observatory Archives, which contain the papers of the Observatory and its directors from c. 1830-1945.

The collection of Leiden University Library also includes the scientific papers of Jan Oort (director of the Observatory from 1945-1970).

Separated Materials

Papers related to Bakhuyzen’s geodetic work can be found in the archive of the Rijkscommissie voor Geodesie in Delft.

The images can be seen on the website of Leiden University Library (AFA FC NCG).


  • [Gent, R. van], De reizende astronoom. Nederlandse sterrenkundige expedities naar de Oost en de West (Leiden 1993).
  • Herk, G. van, H. Kleibrink en W. Bijleveld, De Leidse sterrewacht. Vier eeuwen wacht bij dag en nacht (Zwolle 1983).
  • Lunteren, F. van, Van de Sande Bakhuyzen, Hendricus Gerardus in: T. Hockey (eds.), Biographical Encyclopedia of Astronomers (New York 2007).
  • Sitter, W. de, Short history of the observatory of the university at Leiden 1633-1933 (Haarlem 1933).
  • Baneke, D., Een fotoalbum van formaat, Zenit, Juli/Augustus 2010, 321-327.

Processing Information

The papers have been reordered and repacked. Most of the files were created by Bakhuyzen himself or by his successor E.F. van de Sande Bakhuyzen. The original files were maintained as much as possible. Obviously misfiled papers have been refiled, and obviously related papers have been put together, while obviously unrelated papers have been separated.

Collection guide of the Leiden University archives, Observatory, directorate H.G. van de Sande Bakhuyzen (c. 1873-1923)
Archieven van de Universiteit Leiden - Sterrenwacht, directoraat H.G. van de Sande Bakhuyzen
David Baneke, 2010
Language of description
Script of description
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Language of description note
Beschrijving is in het Engels.

Revision Statements

  • 14 July 2022: latest update

Repository Details

Part of the Leiden University Libraries Archives & Collections Repository

Witte Singel 27
Leiden 2311 BG Netherlands
+31 71 527 2857