Maximilianus Hell (1720-1792) - Munin

Although the observations of Sajnovics and Hell were almost identical, the moments recorded
by Borchgrevink diverged by several seconds from the two Jesuits. Planman of course noticed
this fact, and noted to Wargentin that “besides, the observations of Mister Borgrewing match
my own accurately, if a solar parallax of 8.3 arc seconds is supposed. That satisfies me.” 99
Anders Johan (Andreas Joannes, André Jean) Lexell (1740-1784) was born and raised in
Åbo, where he attended university and was noticed for his brilliance in mathematics. No
positions were vacant in Swedish universities, however, and it may be that he had higher
ambitions as well. Be that as it may, in 1768, he sent two treatises of mathematics to the
Imperial Academy in St. Petersburg. Leonard Euler examined them and made sure that Lexell
obtained a position as his adjunctus (assistant) at the Academy. One of Lexell’s first tasks was
to observe the transit of Venus from the academy building. He did so along with the secretary
of the academy J. A. Euler, the Jesuit Mayer and his assistant Stahl SJ. 100 Having gained
access to the observations from St. Petersburg, Planman commented in a letter to J. A. Euler
that the observations of Lexell matched his own best, under the precondition that the solar
parallax was 8.3 arc seconds. 101
Unlike Planman, however, Lexell was not convinced of the accuracy of his own observation –
or of a solar parallax of 8.3 arc seconds for that matter. He was soon entrusted the task of
calculating the solar parallax on the basis of the observations of 1769. In this process, Lexell
declined all temptation to accord the St. Petersburg observations any special reliability. Quite
the contrary, in a letter to Planman dated 25 June 1770, Lexell said that: 102
99 r
Ibid.: “dessutom instämma H Borgrewings observationer accurat med mina, posita Parallaxi ʘ = 8″,3: och
dermed är jag till freds.”
100
Stahl and Lexell used comparatively small telescopes, while the two largest and best were used by Euler and
Mayer (cf. Mayer 1769a).
101
Planman to Jean Albert Euler in St. Petersburg, dated Åbo 26 September 1769 (copy in Planman’s
handwriting, CVH Stockholm): “Ut autem hæc mea observatio cum Vestris Petropolitanis comparari posset;
supputandus erat effectus Parallaxeos respectu horum locorum. Assumta itaque Parallaxi Solis = 8″,3 quam ex
observationibus transitus anni 1761 obtinui, inveni, facta supputatione, emersionem totalem fieri debuisse 22″
citius Cajaneburgi, quam Petropoli [...]. Mea itaque observatio ad Lexellianam proxime accedit, a Mayeriana
autem maxime discrepat” = “In order to be able to compare my observation with yours from St. Petersburg, it
was necessary to calculate the effect of parallax with regard to these places. Assuming a solar parallax of 8.3 arc
seconds, which I obtained from the observations of the transit in 1761, I found that, after calculation, the total
emersion should have taken place 22 seconds earlier in Cajaneborg than in St. Petersburg [...]. Thus, my
observation is closest to that of Lexell and least in harmony with that of [Christianus] Mayer”.
102
Lexell to Planman in Åbo, dated St. Petersburg 25 June 1770 (HUB Helsinki, Planman-samlingen no. 61,
transcript generously provided by Johan Stén): “Hwad Pater Hells observationer för de bägge siste contactus
angår wet jag ei hwad jag skal säga, han har tör hända fabricerat dem efter de Petersburgiska, och då har han ei
just warit mycket lyckeligt, ty wåra observationer äro säkert ei af de accurataste.”
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