The Dutch Transit of Venus Expeditions of 1874 and 1882

Robert van Gent, Anne Zandstra,Hans Hooijmaijers & Klaus Staubermann

The visibility circumstances of the transit of Venus of 9 December 1874

End of the transit6:26 UT

Begin of the transit1:49 UT

Frederik Kaiser (1808-1872) Volkert S.M. van der Willigen (1822-1878)

Transit of Venus expedition to Réunion (1874)

Location: Saint Denis, Ile de la Réunion (Indian Ocean)Longitude 55° 27' 01.1" EastLatitude 20° 51' 35.3" South

• Jean Abraham Chrétien Oudemans (1827-1906): Chief astronomer. Head Geodetic Survey of Java. Trained by Frederik Kaiser (director of Leiden Observatory from 1837 to 1872). Director of Utrecht Observatory from 1876 to 1895.

• Pieter Jan Kaiser (1838-1916): Astronomer responsible for the photographic observations. Head Department of Verification of Nautical Instruments. Son of Frederik Kaiser.

• Ernst Frederik van de Sande Bakhuyzen (1848-1918): Astronomer. Younger brother of Hendrik Gerard van de Sande Bakhuyzen (director of Leiden Observatory from 1872 to 1908). Director of Leiden Observatory from 1908 to 1918.

• Hendrik Theodorus Soeters (1842-1879): Assistant of J.A.C. Oudemans. Engineer Geodetic Survey of Java.

• Marinus Bernardus Rost van Tonningen (1852-1927): Photographer assigned to assist P.J. Kaiser.

• T.F. Blanken: First mate. Dealt with shipping matters and other odd jobs.

Shipping routes of the Compagnie des Messageries Maritimes (Archives Leiden Observatory)

Main Instruments carried to Réunion (1874)

• Photoheliograph by Dallmeyer (Teyler's Stichting, Haarlem)• Refractor by Utzschneider & Fraunhofer (Mrs. de Beaufort-Stoop)• Merz heliometer (Hollandsche Maatschappij der Wetenschappen/Haarlem & Bataafsch

Genootschap/Rotterdam)• Steinheil refractor (Leiden Observatory)• Airy double-image micrometer (Leiden Observatory)• Astronomical timekeeper by Fraunhofer & Utzschneider (Leiden Observatory)• 14 chronometers (Topographical Survey of Java: Hohwü 394, 455, 502 & 514, Schmidt

325 & 334; Teyler's Stichting: Knoblich 1700; Leiden Observatory: Kiek & Casseres 547, 549 & 556, Hohwü 568, 591 & 594, Arnold 418)

• 2 universal instruments (Topographical Survey of Java: Repsold and Pistor & Martins)• 3 heliotropes (Leiden Observatory & Polytechnic Institute Delft)• 2 models of the transit of Venus by Boosman (Leiden Observatory)

Refractor by Utzschneider& Fraunhofer lent by mrs. Anna Alida de Beaufort-Stoop

Ø = 9.6 cm; f = 160 cm

Museum Boerhaave, Leiden

Chronometer by Knoblich & Krille (Altona)

Teylers Museum, Haarlem

Model of a Transit of Venus by Willem Boosman (Museum Boerhaave, Leiden)

P.J. Kaiser’s 1862 thesis on the use of photography in astronomy

Photoheliograph by John Henry Dallmeyer (London)

Ø = 10.0 cm, f = 230 cmPlate size = 16.3 × 16.3 cm

Mounting by H. Olland (Utrecht)

Teylers Museum, Haarlem

Plate measuring engine by Repsold & Söhne (Museum Boerhaave, Leiden)

Sketch map of Reunion (Archives Leiden Observatory)

Sketch map of Saint-Denis

Archives Leiden Observatory

Living quarters in Saint-Denis (Archives Utrecht Observatory)

The members of the 1874 transit of Venus expeditionStanding (f.l.t.r.): P.J. Kaiser, M.B. Rost van Tonningen, T.F. Blanken(?) Seated (f.l.t.r.): J.A.C. Oudemans, H.T. Soeters(?), E.F. van de Sande Bakhuyzen

Observation camp in Saint-Denis (Archives Utrecht Observatory)

Observation camp in Saint-Denis (Archives Utrecht Observatory)

Present-day view of the observation camp (photograph Dominique Tournès)

“A day with the natives” (Archives Utrecht Observatory)

Telegram & transcript of the results (Archives Leiden Observatory)

The visibility circumstances of the transit of Venus of 6 December 1882

End of the transit20:15 UT

Begin of the transit13:57 UT

Transit of Venus expedition to Curaçao (1882)

Location: Fort Nassau, Willemstad, Curaçao (West Indies)Longitude 68° 56' 17" WestLatitude 12° 07' 30" North

• Paulus Hendricus Brocx (1856-1933): Chief observer. Naval officer 2nd class. Son of Lodewijk Gerard Brocx, Minister of Naval Affairs from 1868 to 1873.

• Pieter Cornelis Swaan (1857-1931): Assistant. Naval officer 2nd class.• H. Lelyveld: Assistant. Second mate.

Propeller steam ship 3rd class Alkmaar (Maritime Museum, Amsterdam)