Observation of the 1761-transit of Venus in Siberia

The site of the Observatory of Chappe d'Auteroche on a hill near the town of Tobolsk

     Les Habitants de cette Ville , peu accoutumés à voir des Etrangers, avoient été étonnés de mon arrivée: ils avoient vu mon Observatoire s'élever aussi-tôt; il étoit d'une forme très différente de celle de leurs bâtiments. Ils y trouverent du mystere. Sa situation sur une montagne, d'où je découvrois tout l'horison, les surprit beaucoup. Il étoit d'ailleurs à un quart de lieu de la Ville. (Chappe d'Auteroche, Voyage en Sibérie, A Amsterdam, Chez Marc Michel Rey, 1769, p. 126).

View (12 October 2005) of the East-horizon from the hill where upon Chappe's observatory was built

View (12 October 2005) of the W-horizon from the hill where upon Chappe's observatory was built

     

The Observatory of Chappe d'Auteroche at Tobolsk

     Actually I started my search from our hotel SIBIR, passing by the Museum of Art, and moving more downwards viewing the small path that led to the monument of ERMAK. I counted carefully my steps walking down, from the residential and higher part of the city, towards the lower and older part. I searched first on a hill, that was not far away from the Polish Church. With a barometer I estimated its height (55m), which was almost the same as the height of the residential part of the city (25 toises = 50m) from which I assumed, that it was once a part of the mountain where upon the city of Tobolsk had been built. However on the top of it, I could only distinguish the Western horizon. The Eastern horizon was covered by another chain of hills, about 200m southwards. At that moment I remembered, when I was with our interpreter for making some pictures from below the town, that I had seen a kind of a plateau on the chain of hills that was situated much closer to the older part of the city (and that had prevented me to see the Eastern horizon). The night was falling fast and I had taken already some risks by mounting upon the first hill, so I decided to return to the hotel.

     The next and sadly our last day of our stay in Tobolsk, I came back to to the second hill (rather a chain of hills) and found a small way that led nicely to the plateau that I had seen from below the street. When I arrived upon this plateau, I felt immediately that I stood at the place where Chappe had erected his observatory, since I could distinguish now the entire horizon from East to West, with the Yrtish river flowing quietly in the West.

      Le calme & la sérénité de l'air m'avoient déterminé à transporter mes instruments hors de de l'Observatoire, pour les mouvoir plus facilement. J'apperçus bien-tôt un des bords du Soleil: c'étoit le temps où Vénus devoit entrer sur cet Astre, mais vers le bord opposé. Ce bord étoit encore dans les nuages. Immobile, & l'oeuil fixé à ma Lunette, mes désirs parcourent un million de fois à chaque instant, l'espace immense qui me sépare de cet Astre. Que ce nuage tardoit à disparoître! Il se dissipe: enfin j'apperçois Vénus entrée sur le Soleil, & je me dispose à observer la phase essentielle (l'entrée totale). Quoique le Ciel soit parfaitement sérein, la crainte trouble encore mes plaisirs.Ce moment approche: un frémissement s'empare de tous mes membres; il faut que je fasse usage de tout mon observation. J'observe enfin cette phase, & un avertissement intérieur m'assure de l'exactitude de mon opération. On peut goùter quelquesfois des plaisirs aussi vifs: mais je jouis dans ce moment de celui de mon observation, & de l'espérance qu'après ma mort la postérité jouira encore de l'avantage qui en doit résulter. (Id, p. 133).

The author at the site of Chappe's Observatory

          
Observations by Chappe (1761)        Observation of the Venus_transit (2004, Elst)     Sunset in Tobolsk (12 October 2005)

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