José Monteiro da Rocha (1734–1819) and His 1782 Work on the Determination of Comet Orbits

In 1782 José Monteiro da Rocha, astronomer and professor at the University of Coimbra, presented, in a public session of the Royal Academy of Sciences of Lisbon, a memoire on the problem of the determination of the orbits of comets. Only in 1799 would the “ Determinação das Orbitas dos Cometas” (Determination of the orbits of comets) be published in the Academy’s memoires. In that work, Monteiro da Rocha presents a method for solving the problem of the determination of the parabolic orbit of a comet making use of three observations. Monteiro da Rocha’s method is essentially the same as the method proposed by Olbers and published under von Zach’s sponsorship 2 years before, in 1797. Having been written and published in Portuguese was certainly a hindrance for its dissemination among the international astronomical community. In this paper, we intend to present Monteiro da Rocha’s method and try to explain to what extent we can justify Gomes Teixeira’s assertion that Monteiro da Rocha and Olbers must figure together in the history of astronomy, as the first inventors of a practical and easy method for the determination of parabolic orbits of comets.